Windows:

Tips

Obscuration

• Ways to stop prying eyes include film, tints, etching, fabrics, lighting, shutters, bricking up, moving windows, and screen walls or obstacles to create standoff outside.
• Reflective film works best with external lighting to prevent indoors being anywhere near as bright.
• Screen printed films rely on confusing the eyes of the watcher. By using black colour on the inside face of the film it is easier for you to see out.
• Vision control film lets you see out at one angle yet block a watcher from outside at the same angle.
• Any film could risk damaging glass if frames are steel and glass is over 10mm thick, so they are often not great for security windows.
• Electric glass obscures in both directions so may not suit your own surveillance of outside and relies on power that you might no longer have.
• Blast curtains obscure slightly in both directions but hide you more than they hide watchers, although are expensive and need a lot of washing as they are white.
• You might find a manufacturer able to fit a blind inside a multiple glazed unit.
• You can obscure windows by lighting outside at least seven times brighter than inside, but this may be difficult within the law (EPA90 s79 & CNEA2005) or without upsetting neighbours or running out of power in grid-down scenarios.
• Partial obscuration works best the darker the inside, which also helps you see out. Increasing external lighting is not as effective.
• Increasing standoff increases visual veiling reflections making it hard for the eye to penetration the window.
• Net curtains only work during daylight unless you operate in the dark at home, and need to be fine mesh and at least double width for folds.
• Have black landscape fabric and duck tape ready to cover windows from prying eyes. Foil also works but is too obvious, static cling is better as it is black but still looks slightly odd. More permanent options include made to measure blackout rollers or paper concertinas, but without special frames they leak, and blackout curtains always leak even with special brackets. A cheaper discreet more reliable made to measure option is velcro covers such as Blackout EZ, which can be slapped on in an emergency without fiddling with tape, looks like a black blind and doesn’t leak. There is a lockdown version of this sort of product, the Nightlock Safety Shade, that fits above the window ready to pull down in an emergency.
• Keep windows closed to prevent overhearing about your preps.

• Ideally a secure building would not have any windows, at least not on the ground floor. Other reasons to hate windows are, unlike walls, that they do not provide obscuration, deterrence (unless security rated) or sensor mounting. You need a way to obscure them and strengthen any at ground level. If you cannot brick up a window then seal it, and if you cannot seal it then lock it, and anyway alarm it. You can worry less about reinforcing windows from 2^nd floor upwards if they do not have climbing routes. You could use air con and extractor fans to avoid opening lights downstairs, and rely on doors as emergency exits, with lockable opening lights upstairs for emergency escape. Whether you can make it fit any building codes is another story, but once you accept fixed lights you can achieve high security ratings.

Window types

• Louvre windows are pretty useless for security, but until replaced could be reglazed with laminated glass and glued in. Even then they can be cut out and the lack of horizontal frames leaves them horribly vulnerable. In hot countries where the ventilation is needed they are tolerated with aluminium bars or polycarbonate slats added inside, but no such products are security rated. Such combinations stop schoolboy burglars but not a tooled up desperado. If you must keep louvres then the only way to get rated security whilst still using them is by ignoring them and relying on the addition of bars or a grille, or secondary glazing or shutter for when closed.

• Try to avoid skylights. Firstly, homeowners like to let the light flood in without obscuration – a security no-no. Secondly, they give intruders the advantage of gravity for tools, so need to be extra strong and thus extra expensive to make a real deterrent. If you must have a skylight you can buy security rated versions from Glazing Vision (up to LPS2081 SRB) and The Rooflight Company (eg Conservation Plateau up to SR3).
• Operable windows or opening lights are bad news in blasts or manual attacks, and are expensive, as how will frames take the weight and where will locks fit?

Vulnerabilities

• UK burglars’ most popular method is unlocked openings, next is forcing locked ones and third comes smashing glass, especially in strong frames ie that could not be forced. Other methods include barging past you, blagging their way in or getting hold of a key. So as well as key security, heightened suspicion and door limiters, you could do with auto-deadlocking openings, strong frames, and glazing to match – as weak frames don’t need strong glass as burglars will open the whole thing with a screwdriver without making much noise or cutting themselves. The sad fact is that rather than replacing annealed glass with laminated glass, the priority is stronger frames that can take a lock. Even small screws (pulled sideways rather than straight back out) can hold a window lock stronger than a wooden frame, which can splinter off in front of the screw, leaving the lock on the opening light and the keep flying off with the sliver of frame. For example, hinge guards held on with three small screws have been tested on uPVC windows that do not fail until the plastic explodes under more than 700kg tension. Unfortunately, standard uPVC windows come with weak friction hinges and espagnolette mushroom cams which can be popped one at a time with a long screwdriver.
• Exposed fittings are bad news, like visible hinge pins, or gaps around edges for tools or to lever out a sash, and weathering or loose beading need attention. Beading may need reinforcing with screws, clips or tape, especially if external. Putty should be avoided. Consider how much gap there is around the frame to shear fixings to the wall and how easily access could be gained to frame screws; in security windows these might come with steel covers that wrap around the brick reveal to delay finding fixings, and steel rings around the bolts in case they find them. Other upgrades you can make include laminated glass, espagnolette locks, hinge bolts and frame covers.

Fixings

• As a minimum for domestic security, ensure you have corner fixings for window and door frames between 150-250mm from corners and fixings at 600m centres between that.

Locks

• Locks fitted to normal windows reduce burglary by a third compared to deadlocks on doors which reduce it by over half, showing that normal windows are too weak to secure properly but window locks are better than nothing. Rim locks on wooden casements suffer from screws able to be pulled straight out, or wood splintering if pulled sideways; on UPVC there is the question what are you fixing into; on aluminium you are screwing into thin soft metal. The best alternatives are continuous multipoints, or sashes which can mainly only be levered against a lock which is either morticed or uses screws pulled sideways. That is one reason why high security windows tend to be sashes or fixed, the other being that high security is an expensive specialist business focussed in the conservation market for listed buildings where you may be banned from fitting casements.

• Sliding sash windows can have a ventilation lock set at 100mm but this is only for when you are at home and not expecting someone to reach in with a standard key, or, worse, a jack.
• UPVC windows and French doors can have sash stoppers fitted, which also come in external key versions such as SashStop, although could thus be opened by turning the spindle if the tumbler was ripped out or by breaking the glass. Insist on a locking version that can’t be flicked open. Most locksmith videos are in error as they screw into plastic, which only gives a maximum pull strength of about 100kg when even PAS24 requires 300kg; you need as a minimum to tap into steel reinforcement and ideally to use a jack plug (assuming there is depth inside the frame). The benefit of the SashStop is it bolts through the frame, even the version without an external key. They also claimed to have a similar door limiter.

• Externally beaded double glazing can be locked to the frame with NoGo glass locks at £30 for four, or with SBD rated GT Snaplock glazing clips at £2 each.

• If keeping normal windows then look at suppliers like Mighton who do glazing tape, restrictors, fasteners and locks. Also consider a Sold Secure Silver Jackloc Titan window restrictor for £30. Window lock types include Jacklok restrictors, sash bolts, locking fitches, sash jammers, snaplocks, catch locks, swing locks, met locks, rack bolts, fanlight locks & pivot locks, ranging from £5-55. All suffer from the challenge there is not much to cut into or bolt through. Brands include the usual suspects and DGS (hinge guards, restrictors, espags & handles), Mila (hinge guards, restrictors, espags & handles), Rola (stops, casement locks & Crittal), Titon (restrictors, espags & handles), Asec (handles) & Banham (sash & casement locks).
• Windows over 600mm long need two locking points.

Sizing lights

• In pricing fabrication of security windows, heavy glazing (over 110kg), small plates (under six square feet), or multiple glazing materials costs disproportionately more as they use extra staff. So if cost is key then you want big thin single glazed windows. However, big spans means thick plates, which cost more in materials except to the extent they avoid as many laminations, and lightweight glazing means poly glass which can put the price through the roof. But for maximum security you would not want multiple panes or opening lights anyway – security windows normally stick fake transoms and mullions over the glass instead. Extreme aspect ratios or unbalanced layups increase delamination over time.

Building regulations

• When choosing windows you might also have requirements for sound, light, heat, fire and wind, eg can you get smoke and people out in a fire?
• Building regulations set a lower strength standard for windows compared to doors, demanding only PAS24 (which is EN1627 RC2N + UK tests), LPS1175 SR1, LPS2081 SRA, STS202 BR1 or STS204 (PAS24 duplicate), whereas doors need LPS1175 SR2, LPS2081 SRB, STS201 or STS202 BR2. SBD advises that STS202 and LPS1175 are higher standards than the rest, ie LPS2081, PAS24, STS201 & STS204, as STS202 & LPS1175 test glazing and require 16.5mm laminated glass compared to at most 6.8mm for PAS24.
• There are also environment standards to meet on fire escape, ventilation and insulation. These are building regulations which can be met as a safe harbour by following approved documents B (fire), F (ventilation) and L (insulation), but you can always propose alternatives to building control.
• You can navigate around building regulations on fire by avoiding egress windows in non-habitable rooms, ground floor habitable rooms with an external door or a door to a hall with an external door, and first floor habitable rooms with floors below 4.5m with a door to a protected stairway (with 30 min fire doors) ending in an external door. Windows above 4.5m such as second floor and above cannot rely on openings for escape as instead those habitable rooms need a protected staircase, so perversely these lower security risk windows can be fixed. Although the ground floor does not normally need fire doors for its rooms, it does if upper floors escape through it, which is almost certainly the case. This means you can have no windows or fixed windows as long as rooms have their own exit door or door to a room with an exit such as the hall. If you choose egress windows then the opening needs to be within 1.1m of the floor with 0.33m2′ free area’ at least 45cm high and 45cm wide which you can jump through and stays open on its own, eg friction hinges. Unfortunately, existing escape windows can only be replaced with escape windows of at least statutory size. There is a catch with using the hall as an escape route to avoid escape windows: the external door must not require a key or PIN etc and can at most only have one step and cannot be glazed with thermoplastic (like polycarbonate). However, it is easier to make a door resist penetration for manipulation of handles than a window. Building control might argue that the escape door can reasonably practicably open outwards.
• You can navigate around building regulations on insulation by:
  • increasing insulation elsewhere to offset a shortfall in window u-value, eg add more loft insulation,
  • commissioning low-e glass double or triple glazed units filled with argon using warm spacers,
  • giving up and just specify for security and fit secondary eco glazing behind it,
  • making do with eco windows and get your security from shutters and/or grilles or security secondary glazing.
• The standard is 1.6W/m2K for new build and 1.4W/m2K for replacement windows. The challenge is that the u-value of old fashioned double glazing is about 100% too high, and even modern aluminium low-e double glazing with warm spacers and argon comes in at about 1.7W/m2K. Even worse, security windows tend to use steel which will not have multiple chambers like uPVC, nor can it have a plastic thermal breaks like aluminium non security windows. Frames are several times worse at insulation than glazing, even in the latest designs, but security frames are even worse.
• You can navigate around building regulations on ventilation for new builds to avoid trickle vents for background ventilation by using fans or offset airbricks to provide the necessary 0.3l/s/m2 above 1.7m from the floor. The regs slightly insanely demand 8,000mm2 trickle vent per habitable room, which is nearly a 4″x4″ hole in a window, basically a hand hole. Bizarrely it also requires a 1cm gap under internal doors even if fire or security doors. However, when replacing windows you need only leave ventilation as good as it was, so a night latch setting, fan or trickle vent smaller than 8,000mm2 might be enough for background ventilation. For purge ventilation you can use extractors instead of opening lights to hit the target of four air changes per hour, which if by opening light for most window types needs to be 1/20th of floor area.
• Just to make life harder, there is also a lesser spoken of approved document O on overheating which may require a different size window than for fire escape and purge ventilation in order to purge heat and limit summer solar gains. You might be able to argue that you need a smaller window on a southern aspect to avoid overheating, but building control may say you need a bigger one to get a big enough free area to purge heat than you do to purge air. Anyway you probably want bigger southern windows to reduce winter heating bills and you could fit shades, shutters, solar control glass, louvres or extractors, and could use air con if all else fails. The standard is typically a maximum of 15% floor area glazed and 22% or 30% for the most glazed room, and a free area of the greater of 6% of floor area and 70% of glazing area, or 4% (13% in central London & Manchester) of floor area for bedrooms. You can argue for solutions that mitigate risk of noise, pollution, security, falls or entrapment. Security and pollution are certainly a risk in a bedroom, where a typical 200 square footage demands an 8 (or 26 in central London & Manchester) square feet opening in the window, equivalent to half or one and half doors wide open in a high crime high pollution area, leaving you little choice but to buy insulation and air con to have any kind of window security.

Summary

• In short, with enough wall thickness to attach to, you can harden windows with any or all of collapsible grilles, roller shutters, polycarbonate or perforated steel shields, security windows and security secondary glazing. With few high rated products on the market, the approach is more likely to be layers of security to slow down intruders against different tools. In security terms, ideally you want to force a burglar to hack through a roller shutter, then lever open a security window, then saw through secondary glazing, and finally cut through a grille, but it costs and does not look great. If at home this could give you time to close internal grilles even if someone beats you to a external shutter; either way it could avoid you being left with no security if you leave one window element open. In some countries grilles and roller shutters are normal for the weather or crime rate, and grilles are common for patio doors in the UK. Polycarbonate shields or secondary glazing avoid the standout nature of roller shutters although the latter can be sometimes be fitted internally anyway, and collapsible grilles do not have to be closed during peacetime.
• The key takeaway from the below data is that the typical home with one brick thick or cavity walls needs glazing equivalent to LPS1270 003 (explained below) such as ESG 22.5mm laminated glass, Tecdur 14mm polycarbonate glass (or 10mm Hammerglass polycarbonate if not bothered about weathering) to ensure continuous strength against manual attack, while a half brick thick garage needs glazing equivalent to LPS1270 002 such as ESG Secure 20.5mm laminated glass, 18mm poly glass (or 8mm Hammerglass poly). Glazing to SR2 or SR3 can be made up as double glazed units. Adding blast or ballistic ratings will add thickness. Unless you have a panic room with security panels or a house built of stone or reinforced concrete you do not need poly thicker than 10mm (unless you fear chemical attack) or glass thicker than about 20mm unless you want to deter or delay attackers who prefer windows to the obstacles, noise and visibility of coming through walls. However, eventually, especially as breeze blocks are mostly fresh air and some bricks are partly hollow, there is the question of whether the wall fixings will fail or be chopped out before the glazing gives in. The next question is where will the frames come from? You will have to either have them made and hope they are equivalent to SR1/2/3 as required, or buy ready made from Hampton Conservatories or Crittall Fendor, or buy an EU window to EN1627 and have the manufacturer upgrade the glazing to a glass attack standard beyond RC3. Particularly if you are happy to beef up window security with a grille or shutter or secondary glazing there is a fourth option: buy the strongest consumer market window you can find and try to upgrade the glazing. The strongest the author has found is Rehau Geneo, rated up to RC3, into which glass fibre (and steel if RC3) reinforced uPVC frames you could insert insurance rated sealed units using the 53mm space allowed for triple glazing; as standard they would need only come with P5A glazing such as 10.3mm laminated glass. Obviously there is no guarantee that glazing stronger than P5A cannot be pried out of the rebates of even steel reinforced upvc frames, but this way you could get a window approaching SR2 strength without SR2 cost.

Components

Security ranked products

• For the first time ever as far as the author knows, below is a table of standards and products available in the UK (plus overseas ones if offering something special) and layups for manual attack, blast and ballistic, merged in rough strength order, and grouped by matching manual attack wall strength. Beware that if there is no manual attack rating then the fact that a product is the same thickness as another manual attack, ballistic or blast product does not guarantee its manual attack strength. For example, very thick laminated glass is stiff enough to shrug off explosions but not necessarily multiple shots or blows from a gun or pickaxe attacking already cracked glass.

Rating	Product
ASTM F1233 classes 1-3	Up to lam poly 19mm does not survive fire axe, wood splitting maul, acetone or over 16 sequences. Class 1.4 poly 6mm allows body passage after 5m of propane torch; class 2.2 poly 12mm allows body passage after 2m36s of hammering after 5m of propane torch. Class 1 covers 6.9mm-14.3mm lam glass.
UFC very low threat / NIJ 0316.00-80	Laminated glass 6mm / polycarbonate 6mm
USA Navy low protection any threat level	Laminated strengthened glass 6mm
CPSC 16 CFR 1201 Cat I / ANSI Z97.1 class B / CAN/CGSB class B	Laminated glass 6.4mm
EN12600 2B2	Saint Gobain Stadip 6.4mm laminated glass
	Ionomer glass 6.9mm (Sentryglas Xtra interlayer) fails EN356 P1A
EN12600 1B1	Saint Gobain Stadip 7mm laminated glass
EN356 P1A	Ionomer glass: 6.8mm (Sentryglas interlayer), or 6.8mm (Sentryglas Xtra interlayer); Laminated glass: Saint Gobain Stadip Protect 6.8mm
EN356 P2A / SBD / PAS24 / P1A	Laminated glass: ESG Secure laminated glass 6.8mm, or Saint Gobain Stadip Protect 8.8mm, or Tecdur laminated glass 8.4mm P1A, or Tecdur laminated glass 8.8mm P2A
UL972 / UFC very low threat	Laminated glass: Secur-Lite laminated glass 8mm, or Laminated glass 7.5mm (3mm+1.52mm+3m)
ASTM F1233 4	(UFC very low threat)
HPW TP-0500.02 II-III	(UFC very low threat)
EN356 P3A	Laminated glass: Tecdur laminated glass 9.1mm, or ESG Secure laminated glass 9.2mm, or Saint Gobain Stadip Protect 9.1mm
EN356 P4A / EN1627 RC2 (glass not attacked)	Laminated glass: ESG Secure laminated glass 9.5mm, or Tecdur laminated glass 9.5mm, or Saint Gobain Stadip Protect 9.5mm; Poly glass: Sicurtec Attack poly glass 9mm RC2, or Silatec RC2 Panic 16mm poly glass (EUR393/m2)
EN13541 ER1 S	Saint Gobain Vetrotech Vetrogard / Stadip Protect BS laminated glass 10mm
EN356 P5A / EN1627 RC3 (glass not attacked)	Laminated glass: ESG Secure laminated glass 10.3mm, or Tecdur laminated glass 10.3mm, or Saint Gobain Stadip Protect SP / Vetrotech Vetrogard 10mm; Poly glass: Sicurteck Attack poly glass 10mm RC3, or Silatec RC3 Panic 28mm (EUR678/m2), or Sicurtec Slim 7mm poly glass
LPS2081 SRA / PAS24 / STS 204 / P4A	Laminated glass 11.5mm No products at SRA
LPS2081 SRB	No products
EN1063 BR1 S	Saint Gobain Vetrotech Vetrogard / Stadip Protect HS laminated glass 13mm
EN356 P6B / EN1627 RC4 (glass not attacked)	RvE oak window; Hammergard poly 4mm; Laminated glass: Laminated glass 23mm with Trosifol PVB interlayer (3mm + 1.52mm + 10mm + 2.28mm + 5mm), or ESG Secure laminated glass 11mm LPS1270 001, or Tecdur laminated glass 11mm, or Pilkington Optilam laminated glass 15mm, or Saint Gobain Stadip Protect SP / Vetrotech Vetrogard 15mm laminated glass; Poly glass: Tecdur poly glass 9.5mm, or Sicurtec Attack poly glass 16mm RC4, or Sicurtec 15mm P6B poly glass, or Vetrotech Polygard poly glass 15mm, or Silatec 16mm, or Silatec RC4 Panic poly glass 40mm (EUR950/m2, + BR4 NS EUR1,378/m2), or Sicurtec Slim 10mm
23kg TNT at 20m on 1m x 1m window	Laminated tempered glass 9mm + 9mm, Polycarbonate 16mm
EN13541 ER1 NS	Saint Gobain Stadip Protect BS / Vetrotech Vetrogard laminated glass 18mm; Poly glass: Sicurtec Blast 13mm poly glass, or Hammerglass 12mm
EN13541 ER2 S	Saint Gobain Stadip Protect BS / Vetrotech Vetrogard laminated glass 18mm
AAMA 501.8 psychiatric (2,700J, 200lb dropped 10′)	Ionomer glass 10.43mm with Sentryglas ionomer interlayer & spall layer (4mm + 2.28 + 4mm + 0.15mm)
EN356 P7B	Sommer Sokaltherm 78B+ custody window to RC3; Hammerglass poly 6mm; Polyglass: ESG Secure poly glass 11.3mm LPS1270 001, or Tecdur poly glass 14mm, or Vetrotech Polygard poly glass 15mm, or Silatec poly glass 23mm, or Sicurtec Attack P7B poly glass 19mm; Laminated glass: Tecdur laminated glass 24mm, or Pilkington Optilam laminated glass 22.6mm, or Saint Gobain Vetrotech Vetrogard laminated glass 22mm, Laminated glass 22mm with Trosifol PVB interlayers (4mm + 0.76mm + 8mm + 0.76mm + 5mm + 0.76mm + 3mm), or Ionomer glass 11mm with Sentryglas / Sentryglas Xtra ionoplast interlayer (4mm + 3.04mm + 4mm).
UL972 (271J) (UFC very low threat) (can equate to EN256 P1A-P5A)	Tuffak Hygard AR polycarbonate 6mm (+ ASTM F1915 4)
EN356 P8B	Hammerglass poly P8B 8mm; Laminated glass: Saint Gobain Vetrotech Vetrogard laminated glass 27mm, or Tecdur laminated glass 29mm P8A, or Pilkington Optilam laminated glass 39mm, or Laminated glass 28mm with Trosifol PVB interlayers (4mm + 0.76mm + 6mm + 0.76mm + 5mm + 0.76mm + 6mm + 0.76mm + 4mm), or Saint Gobain Stadip Protect SP 25mm laminated glass; Poly glass: Vetrotech Polygard poly glass 17mm, or Tecdur poly glass 16mm LPS1270 001 (SR1), or ESG Secure poly glass 13mm LPS1270 001 & EN1063 BR1, or Silatec poly glass 24mm, or Sicurtec Slim 14mm, or Sicurtec Attack P8B poly glass 22mm; Ionomer glass 12.56 or 16.56mm with Sentryglas / Sentryglas Xtra ionoplast interlayer (4mm + 2.28mm + 4mm + 2.28mm + 4mm, or 4mm + 4.56mm + 4mm); Blast & Ballistics TDSBB 1007 secondary glazing P8B 16.5mm.
ASTM F 1915 3	Tuffak Hygard AR polycarbonate 9.5mm (+ UL972 manual attack)
Wall to SR1	Lightweight concrete block (RC2); 4″ brick (c. RC3); Securilath MD1; Plasterboard faced with 1″ tongue & groove (even if backed by 0.5″ plywood, or lined with 5mm steel (c. D1)) (c. SR1) or 2″ planks (c. SR1, c. H1)
LPS1175 SR1, + glazing EN356 P8B or LPS1270 XX1	Selectaglaze secondary sash, casement & fixed 12.04mm laminated glass; Laminated glass: ESG laminated glass 11.3mm P6B, or ESG Secure 16.5mm & EN1063 BR1, or ESG Secure 16.3mm P8B; Tecdur poly glass 16mm;
UFC low threat 1 minute (low observable handtools, US Navy needs 4″ reinforced concrete wall or equivalent)	0.25” wired glass; 0.25” tempered glass (beware glass breakers); 0.5” acrylic; Ionomer: 20mm layup of 5mm annealed glass + 13mm extruded ionomer + 3mm annealed glass (US Navy low threat), or 22.2mm layup of 4.75mm annealed glass + 12.7mm extruded ionomer + 4.75mm annealed glass; Polycarbonate glass: 17.4 / 19mm layup of 3 / 5mm annealed glass + 10mm polycarbonate + 3 / 5mm annealed glass (US Navy low threat, Navy published wrong figures & probably 3mm annealed is correct); Polycarbonate: 10mm polycarbonate (US Navy low threat), or 12.7mm polycarbonate (eg Lexan MR10 to ASTM F1233 II / ASTM 1915 4 / HPW I); Insulated unit: 18mm IGU of 6mm laminated annealed glass + 6mm air gap + 6mm polycarbonate, or 1″ IGU of 0.25” laminated annealed glass of 3mm + 3mm + ¼” air gap + 0.5” laminated polycarbonate of 1/8″ + 1/4″ + 1/8″, (US Navy low threat), or 35mm IGU of 12.7mm polycarbonate + 16mm air gap + 6.4mm laminated glass.
Sandia 2 minutes against hand tools or 1 minute against thermal attack	0.5″ polycarbonate
UFC low threat 2 minutes (low observable handtools)	0.25” plate glass with 10 gauge (3.1mm) 6”x6” steel mesh cover, 0.25” laminated glass
HPW TP-0502.02 IV-V	(UFC low threat, no sharp tools tested on glazing)
SD-STD.01.01 FE 5 / 15 / 60	(UFC low threat); FEBR15 from 55mm insulated unit of 31mm layup of 0.5” tempered glass + 0.18” SG + 0.5” tempered glass + 0.25” air gap + 18mm layup of 0.25” heat strengthened glass + 0.18 SG + 0.25” heat strengthened glass + 8 mil shatter resistant window film (daylight or edge-to edge application)
ASTM F1233 5	(UFC low threat)
ASTM F1233 HG1 + 1.5 CP + 2.8 BP / ASTM F1915 3 / HPW TP-0500 I + A / UL972	Tuffak Hygard CG375 lam poly 10mm
ASTM F1233 III / ASTM 1915 3 / HPW II / WMFL III	Lexgard MPC375 9.5mm lam poly
HPW II / WMFL III	Sure-Gard ICGCP1316 poly glass 19mm
HPW II / WMFL III / ASTM 1915 3	Patriot Armour GCP750 poly glass 19mm
Wall to SR2	8″ brick (c. C3, c. D1); 8″ reinforced brick (c. D3); 9″ brick (RC4); 4″ + 4″ cavity wall (c. RC3 extended delay); Securilath HD1; 8″ grouted reinforced CMU (c. D1, c. SR2); 12″ ungrouted hollow CMU (c. SR2, c. D1)
LPS1175 SR2, glazing LPS1270 XX2	Hampton Conservatories Sapele fixed light / Quattroglide sash; Sash Window Conservation Sash Secure 240 Embassy; Selectaglaze secondary sash, casement & fixed 12mm Tecdur poly glass or 12.4mm poly glass; (Hammerglass poly 10mm & 12mm has been used in an SR2 door by Premier); Poly glass: Tecdur poly glass 18mm LPS1270 012, or ESG Secure poly glass 18mm LPS1270 112 & EN1063 BR2, or ESG Secure 20.5mm LPS1270 012 & EN1063 BR2, or Tecdur DC28 to DC48 (glass as door vision panel in Stafford Bridge Hendon), or 45mm laminated glass (Charter Global Obexion, Bradbury M2M, Rhino HF & Lincoln Victor third party door vision panel), 12mm (probably poly glass) to 40mm laminated glass (Hampton Conservatories Security Door), or Vistamatic Chieftan / Sherman or Tyneside AB26 door vision panel (Metador Defender Extreme, Sunray Excludor2 can use Sherman), or Excluglass2 (Sunray Excludor2 door vision panel), Tecdur SC14 to LPS1270 123 (4mm toughened glass + 8mm polycarbonate) (Urban Front E80S SR2 door glazing)
UFC medium threat 1 minute (high observable handtools & limited power tools, UFC advises do not specify glazing for medium threat, US Navy needs 6″ reinforced concrete wall or equivalent)	(3 mins level II) 0.5” polycarbonate; (also level II) 0.25” acrylic, Poly glass: 17mm 5-ply poly glass of 5mm annealed + 10mm poly + 5mm annealed (also levels II & IV)), or 24mm layup of 5mm heat strengthened glass + 6mm annealed glass + 9mm lam poly of 3mm + 3mm + 3mm (US Navy medium threat); 32mm 7-ply lam poly of 3mm + 13mm + 13mm + 3mm (US Navy medium threat); Ionomer glass 54mm 10-ply layup of 22mm laminated glass of 9.5mm + 9.5mm + 2.4mm + 25mm ionomer + 2.4mm annealed glass + spall film (US Navy medium threat, Navy published wrong thickness but protected face glass is probably 2.4mm); Insulated unit: 44mm IGU of 6mm 3-ply laminated annealed glass of 3mm + 3mm + 6mm air gap + 32mm 7-ply lam poly of 3mm + 13mm + 13mm + 3mm (US Navy medium threat, Navy published wrong thickness, probably should be 1.25″ lam poly).
NIJ 0108.01 I	Ionomer glass 11.6mm: Annealed 3 mm + Sentryglas ionomer 5 mm + Annealed 2.5mm + Trosifol Ultraclear 0.76mm + Trosifol Spallshield CPET 0.18mm
EN1627 RC5 via EN376 P7B	Salzer S1es aluminium facade
EN1063 BR1 NS	Poly glass: Vetrotech Polygard poly glass 18mm, or Silatech ShooteQ BR1-NS 14/27 poly glass 15mm (P6B), or Sicurtec Bullet 14mm; Laminated glass: Saint Gobain Stadip Protect HS 20mm laminated glass
Wall to SR3	Securilath Ultra; Stone; Brickwork (for firearms security per police); 4″ reinforced concrete (c. SR3); 4″ concrete (c. SR3, c. D3); 4” concrete reinforced with 0.25” gauge 6” square mesh reinforcement (c. SR3, c. D3); 8” grouted no8 rebarred hollow concrete blocks (c. SR3, c. D3); 6” concrete reinforced with no 5 rebars at 6” centres (c. SR3, c. D5); Three layers of 10 gauge (3.2mm) steel plate sandwiching two layers of 0.75” plywood (c. SR3, c. H5).
LPS1175 SR3, glazing LPS1270 XX3	RSG 14000 collapsible grille; Crittal Fendor top hung opening lights; Selectaglaze secondary fixed demountable Tecdur 12mm; R&D Sheet Metal SecureView3 vision panel; Poly 10mm; Poly glass: ESG Secure 22.5mm LPS1270 013 & EN1063 BR2, or ESG Secure poly glass 20mm LPS1270 123 & EN1063 BR2 (or 26mm), or ESG Secure poly glass 31mm LPS1270 223, or Hamilton Erskine poly glass 20mm, or Tecdur poly glass 20mm LPS1270 123, or Tecdur DC28 to DC35 (Stafford Bridge Sandhurst door vision panel), or 45.5mm laminated glass (Charter Global Obexion, Bradbury M2M3, Rhino HF & Lincoln Vigilant II third party door vision panel), or Surelock McGill S-11750-5200 vision panel (steel bolt through cassette) (Robust UK Tuff-Dor3), or ExcluGlass3 (Sunray Excludor3 Mk2 door vision panel), or SentinelLite SR3 (Technocover Sentinel Lite 3 door vision panel)
EN1063 BR2 S	Laminated glass: Vetrotech Vetrogard laminated glass 22mm, or Saint Gobain Stadip Protect HS 19mm laminated glass
EN1063 BR3 S	Saint Gobain Stadip Protect HS / Vetrotech Vetrogard laminated glass 23mm
EN1063 BR3 NS	HardGlass poly glass 21mm; Saint Gobain Stadip Protect HS 49mm laminated glass
EN13541 ER2 NS	Saint Gobain Stadip Protect BS / Vetrotech Vetrogard laminated glass 26mm; Sicurtec Blast 16mm poly glass; Hammerglass 12mm poly
UL972 / ASTM F1233 1.4 CP + 2.0 BP / ASTM F1915 3 / HPW I	Tuffak Hygard AR500 polycarbonate 12.5mm
ASTM F1233 1.4CP + 2.8 BP + HG / HPW A	ArmorPlast50 lam poly 13.5mm
ASTM F1233 III / ASTM 1915 2 / HPW II, WMFL II	Lexgard MPC500 lam poly 12.5mm
HPW A + I / ASTM F 1233 HG1 .38 Special LRN + 1.5 CP + 3.2 BP / ASTM F 1915 3 / HPW TP-0500 1 / UL972	Plaskolite Makrolon Hygard CG500 lam poly 13.5mm three ply (HPW I to sequence 15 only?)
ASTM F1233 IV / ASTM 1915 1 / HPW III	Lexgard RC750 18mm lam poly
UL752 Level I (9mm)	Lam poly: Tuffak Hygard BR750 20mm two ply lam poly (inc 0.5″ acrylic core) (+ UL972 + HPW B), or Lexgard MP750 lam poly 19.5mm; Acrylic: Tuffak Polycast MP acrylic 31mm, or Tuffak Plexiglas SB acrylic 31mm; Secur-Tem+Poly SP175 poly glass 19mm, Ionomer glass 21.6mm: Annealed 6mm + Sentryglas poly 0.9mm + annealed 6mm + Sentryglas 4.5mm + annealed 3mm + Trosifol Ultraclear 0.76mm + Trosifol Spallshield CPET 0.18mm; Laminated glass 31mm; Poly glass: Sicurtec Shield 19mm
ASTM F1233 2.4 CP + 3.5 BP / ASTM F1915 1 / HPW II + B	Tuffak Hygard CG750 lam poly 20mm
ASTM F1233 5 / HPW IV / UL752 2	Lexgard MP1000 25mm lam poly
9mm VPAM 2	Silatec MyGard lam poly 2600
NIJ 0108.01 IIA	Ionomer glass 18mm: Annealed 4mm + Sentryglas 0.9mm + Annealed 4 mm + Sentryglas 5mm + Annealed 2.5 mm + Trosifol Ultraclear 1.5mm + Trosifol Spallshield CPET 0.18mm; Secur-Tem+Poly SP175 poly glass 19mm
100kg TNT at 20m on 1m x 1m window	Laminated tempered glass 12mm + 9mm + 9mm; Polycarbonate 25mm
UL752 Level 2 (.357 magnum)	Lam poly: Tuffak Hygard BR1000 25mm four ply lam poly (+ HPW IV + ASTM F1233 2.4 CP + 5 BP + ASTM F1915 1 + UL972), or Lexgard HP875 lam poly 22mm; Secur-Tem+Poly SP293 24mm poly glass, Tuffak Polycast HP acrylic 35mm; Ionomer glass 22.4mm: Annealed 3 mm + Sentryglas 0.9 mm + Annealed 5 mm + Sentryglas 0.9 mm + Annealed 5mm + SentryGlas 4.5mm + Annealed 3mm + Trosifol Ultraclear 0.76mm + Trosifol Spallshield CPET 0.18 mm; Laminated glass 47mm
USA Navy low threat (9mm handgun)	Insulated unit 21mm of 6mm 3-ply 3mm laminated heat strengthened glass + 6mm air gap + 9mm 5-ply 3mm laminated polycarbonate; 28mm 7-ply laminated glass of 3mm + 6mm + 10mm + 10mm; 25mm 7-ply laminated polycarbonate of 3mm + 10mm + 10mm + 3mm; Polycarbonate glass of: 12mm layup of 6mm 2-ply 3mm chemically strengthened laminated glass + 6mm 2-ply 3mm laminated polycarbonate, or 15mm layup of 6mm heat strengthened glass + 9mm 3-ply 3mm laminated polycarbonate, or 20mm layup of 11mm laminated glass of 5mm heat strengthened glass + 6mm annealed glass + 9mm 3-ply 3mm laminated polycarbonate
EN13541 ER3 S	Saint Gobain Stadip Protect BS / Vetrotech Vetrogard laminated glass 31mm
EN13541 ER3 NS	Sicurtec Blast 18mm poly glass
EN13541 ER4 S	Saint Gobain Stadip Protect BS / Vetrotech Vetrogard laminated glass 27mm
EN1063 BR2 NS	Laminated glass: Vetrotech Vetrogard laminated glass 31mm, or Saint Gobain Stadip Protect HS 34mm laminated glass; Poly glass: Silatech ShooteQ BR2-NS 18/35 poly glass 19mm (P7B), or Sicurtec Bullet 18mm
EN1063 BR4 S	Laminated glass: Vetrotech Vetrogard laminated glass 32mm / Saint Gobain Stadip Protect HS 31mm, or Vetrotech Vetrogard Pro laminated glass 35mm (+SG1 S + P8B)
EN1063 SG1 S	Laminated glass: Vetrotech Vetrogard laminated glass 32mm, or Saint Gobain Stadip Protect HC 33mm laminated glass
EN13541 ER4 NS	Saint Gobain Stadip Protect BS / Vetrotech Vetrogard laminated glass 33mm; Sicurtec Blast 24mm poly glass
EN1063 BR5 S	Laminated glass: Saint Gobain Stadip Protect HS / Vetrotech Vetrogard laminated glass 36mm, or Saint Gobain Stadip Protect FS 34mm laminated glass (+SG1 S + P6B), or Saint Gobain Stadip Protect FS 40mm laminated glass (+SG2 S + P7B)
EN1063 BR3 NS	Laminated glass: Vetrotech Vetrogard laminated glass 44mm, or Vetrotech Vetrogard Pro laminated glass 44mm (+ P8B); Poly glass: Silatech ShooteQ BR3-NS 20/40 poly glass 21mm (P7B), or Sicurtec Bullet 20mm
NIJ 0108.01 II	Ionomer glass 18mm: Annealed 4mm + Sentryglas 0.9mm + Annealed 4 mm + Sentryglas 5mm + Annealed 2.5 mm + Trosifol Ultraclear 1.5mm + Trosifol Spallshield CPET 0.18mm
USA Navy medium threat (.44 magnum)	44mm 9-ply laminated annealed glass of 3mm + 6mm + 12mm + 19mm + 3mm; 31mm 7-ply laminated polycarbonate of 3mm + 6mm + 6mm + 3mm; Insulated unit of: 12mm 3-ply 6mm laminated heat strengthened glass + 6mm air gap + 12mm 3-ply laminated polycarbonate of 3mm + 6mm + 3mm insulated unit, or 6mm 3-ply 3mm laminated heat strengthened glass + 6mm air gap + 19mm 5-ply laminated polycarbonate of 3mm + 13mm + 3mm; Poly glass of: 22mm layup of 10mm 3-ply 5mm chemically strengthened laminated glass + 12mm 5-ply laminated polycarbonate of 3mm + 6mm + 3mm, or 26mm layup of 16mm 3-ply laminated glass of 6mm heat strengthened glass + 10mm annealed glass + 10mm 5-ply 3mm polycarbonate, or 21mm layup of 12mm 3-ply laminated glass of 5mm strengthened glass + 6mm annealed glass + 9mm polycarbonate, or 28mm layup of 22mm 3-ply 11m laminated annealed glass + 6mm polycarbonate, or 28mm layup of 22mm annealed glass + 6mm polycarbonate, or 33mm layup of 11mm 3-ply laminated glass of 3mm heat strengthened glass + 8mm annealed glass + 12mm 5-ply laminated polycarbonate of 3mm + 6mm + 3mm, or 33mm layup of 23mm 5-ply laminated glass of 3mm chemically strengthened glass + 8mm annealed + 8mm annealed + 10mm polycarbonate
230kg TNT at 20m on 1m x 1m window	Laminated tempered glass 16mm + 16mm + 16mm; Polycarbonate 38mm
UL753 3	Ionomer glass 25.4mm: Annealed 4 mm + Sentryglas 0.9 mm + Annealed 6mm + Sentryglas 0.9 mm + Annealed 6mm + Sentryglas 4.5mm + Annealed 3 mm + Trosifol 0.76mm + Trosifol Spallshield CPET 0.18mm, Secur-Tem+Poly SP311 poly glass 28mm; Laminated glass 53mm; Poly glass: Sicurtec Shield 32mm
UFC medium threat 4 minutes (high observable handtools & limited power tools)	Insulated unit: ¼” laminated annealed glass + 1.4” air gap + 1.125” laminated polycarbonate, or 44mm insulated unit of glass + air gap + 32mm laminated polycarbonate; Ionomer: 7/8” laminated annealed glass + 1” extruded ionomer + 3/32” annealed glass, or 54mm ionomer glass including 25mm extruded ionomer, or 22mm laminated annealed glass + 25mm extruded ionomer + 4mm annealed glass; Polycarbonate glass: 3/16” strengthened glass + ¼” annealed glass + 3/8” polycarbonate, or 24mm polycarbonate glass including 12.7mm polycarbonate; Polycarbonate: 1.25” laminated polycarbonate; Lam poly: 32mm laminated polycarbonate (eg Lexguard MP1250 32.5mm (WMFL 1 / ASTM F1233 5 / ASTM 1915 1 / HPW V, / UL752 3), or four ply Hygard BR1250 32mm (UL752 III / NIJ IIIA / HPW IV / ASTM F1915 1 / ASTM F1233 5 BP 2.5 CP), or four ply Lexgard SP1250 (ASTM F1233 V / ASTM F1915 1 / HPW V / WMFL I), or ArmorPlast125 (Ul752 3 / HPW IV / ASTM F1233 V).
UFC medium threat 5 minutes (high observable handtools & limited power tools)	0.25” plate glass with ½” A36 steel bars each way on 6” centres
UFC high threat 5 minutes (power & thermal tools)	(also level III & 15 mins level II) from 13/16” poly glass including 0.5” polycarbonate core
EN1063 BR4 NS	Laminated glass: Saint Gobain Stadip Protect HS / Vetrotech Vetrogard laminated glass 54mm, or Vetrotech Vetrogard Pro laminated glass 54mm (+ P8B); Poly glass: Vetrotech Polygard Pro poly glass 21mm (+ SG1 NS + P8B), or HardGlass poly glass 23mm, or Silatech ShooteQ BR4 NS 25/52 poly glass 25mm (P6B), or Sicurtec Bullet 23mm, or Hammerglass poly 23mm; Ionomer glass 21.3mm (Annealed 6mm + Sentryglas poly 1mm + annealed 6mm + Sentryglas 5mm + annealed 2.5mm + Trosifol Ultraclear 1.52mm + Trosifol Spallshield CPET 0.18mm / SGX can be substituted in same thicknesses)
NIJ 0108.01 IIIA	Ionomer glass 21.4mm (Annealed 6mm + Sentryglas ionomer 0.9mm + annealed 6mm + Sentryglas 5mm + annealed 2.5mm + Trosifol Ultraclear 1.52mm + Trosifol Spallshield poly 0.18mm); Secur-Tem+Poly SP412 poly glass 31mm
EN1063 BR6 S	Laminated glass: Saint Gobain Stadip Protect HS 47mm laminated glass, or Vetrotech Vetrogard laminated glass 50mm, or Saint Gobain Stadip Protect FS 41mm laminated glass (+ SG2 S + P8B) / Vetrotech Vetrogard Pro laminated glass 51mm (+ SG2 S + P8B)
EN1063 SG2 S	Laminated glass: Vetrotech Vetrogard laminated glass 50mm, or Saint Gobain Stadip Protect HC 47mm laminated glass
USA Navy high threat (12 gauge shotgun / 7.62mm rifle 147 grain M80 ball)	52mm 9-ply laminated annealed glass of 3mm + 6mm + 19mm + 19mm + 3mm; Insulated unit of: 49mm IGU of 20mm 3-ply laminated heat strengthened glass of 9.5mm + 9.5mm + 6mm air gap + 24mm 7-ply laminated polycarbonate of 3mm + 12mm + 5mm + 3mm, or 6mm laminated strengthened glass + 6mm air gap + 19mm polycarbonate; Polycarbonate glass of: 35mm layup of 22mm 5-ply laminated glass of 3mm heat strengthened laminated glass + 19mm laminated annealed glass of 9.5mm + 9.5mm + 10mm polycarbonate, or 35mm layup of 25mm 5-ply laminated annealed glass of 3mm + 12mm + 9.5mm + 6mm polycarbonate, or 37mm layup of 28mm 5-ply laminated heat strengthened glass of 3mm + 12mm + 12mm + 5mm polycarbonate, or 41mm layup of 28mm 5-ply laminated annealed glass of 3mm + 12mm + 12mm + 10mm 5-ply laminated polycarbonate of 3mm + 3mm + 3mm; Ionomer glass of 5-ply 0.25″ annealed + 0.1″ SGX poly interlayer + 0.25″ annealed + 0.1″ SGX + 0.25″ annealed + 0.5″ air gap + 6-ply 0.25″ annealed + 0.1″ SGX + 0.25 annealed + 0.1″ SGX + 0.25″ annealed + Madico CL 700 SRB TPU PET film (+ SD-STD.01.01 FEBR 15), or 5-ply 0.25″ annealed + 0.1″ SGX poly interlayer + 0.25″ annealed + 0.1″ SGX + 0.25″ annealed + 0.5″ air gap + 6-ply 0.25″ annealed + 0.1″ SGX + 0.25 annealed + 0.1″ SGX + 0.25″ annealed + Madico CL 700 SRB TPU PET film (+ SD-STD.01.01 FEBR 15), or 3-ply 0.5″ annealed + 0.2″ Trosifol SGX poly interlayer + 0.5″ annealed +0.5″ air gap + 4-ply 0.25″ heat strengthened + 0.2″ SGX + 0.25 heat strengthened + 0.025″ Madico CL 700 SRB TPU PET film (+ SD-STD.01.01 FEBR 15)
VPAM PM6 2007 (7.62 x 39)	Sicurtec Bullet 35mm
UL752 5	Ionomer glass 36.2mm: Annealed 8mm + Trosifol 0.76mm + Annealed 10mm + Trosifol 0.76mm + Annealed 8mm + Sentryglas 5 mm + Annealed 3mm + Trosifol Ultraclear 0.76mm + Trosifol Spallshield CPET 0.18 mm; Secur-Tem+Poly SP513 poly glass 33mm
EN1063 BR4 NS	Vetrotech Vetrogard laminated glass 54mm
G3 AK47	Saint-Gobaine Vetrotech Vetrogard AK47-NS laminated glass 58mm; Silatech ShooteQ AK47-NS 36/76 poly glass 36mm (+VPAM 6 +BR5 NS)
EN1063 BR5 NS	Saint Gobain Stadip Protect HS / Vetrogard laminated glass 58mm; Poly glass: Vetrotech Polygard poly glass 32mm, or Silatech ShooteQ BR5 NS 35/76 poly glass 36mm (+P7B), or Sicurtec Bullet 35mm
460kg TNT at 20m on 1m x 1m window	Laminated tempered glass 16mm + 16mm + 16mm + 16mm; Polycarbonate 54mm
EN1063 SG1 NS	Saint Gobain Stadip Protect HC 71mm laminated glass; Poly glass: Silatech ShooteQ SG1-NS 25/43 poly glass 26mm (+P8B), or Sicurtec Bullet 26mm
UL752 6	Tuffak Hygard MS1250 poly acrylic 36.5mm (+ Shotgun); Ionomer glass 36.5mm: Annealed 8mm + Trosifol 0.76mm + Annealed 10mm + Trosifol 0.76mm + Annealed 8mm + Sentryglas 5 mm + Annealed 3mm + Trosifol Ultraclear 0.76mm + Trosifol Spallshield CPET 0.18 mm; Poly glass: Sicurtec Shield 32mm
EN1063 SG2 NS	Poly glass: Silatech ShooteQ SG2 NS 31/52 poly glass 31mm (+P8B), or Sicurtec Bullet 30mm; Saint Gobain Stadip Protect HC 84mm laminated glass
Wall to SR4	Warriorscreen; Safetell Citywall; Burton Talos; 13″ brick (for firearms security per police); 8” concrete reinforced with two layers of 0.25” gauge 6” square mesh (c. SR4); Three layers of 0.25” stainless steel protecting 0.5” polycarbonate backed by one layer of 10 gauge (3.1mm) low alloy steel plate (c. SR4, c. H10); Five layers of 10 gauge steel plate protecting 0.75” plywood backed by a layer of 10 gauge steel plate and another 0.75” plywood and another layer of 10 gauge steel plate (c. SR4, c. H10); Three layers of 9 gauge (3.7mm) low alloy steel plate protecting 0.75” plywood backed by one layer of 9 gauge (3.5mm) low alloy steel plate (c. SR4, c. H10); 9mm steel mesh lining a reinforced concrete wall can add 14 minutes penetration time against medium threat heavy hand and battery tools (c. SR4, c. F10).
LPS1175 SR4, glazing LPS1270 XX4	Crittal Fendor Secureline fixed; R&D Sheet Metal SecureView4 vision panel; Poly glass: Tecdur poly glass 34mm LPS1270 234, or ESG Secure poly glass 39mm LPS1270 224 & EN1063 BR4, or ESG Secure poly glass 42mm LPS1270 224 & EN1063 BR4, or ESG Secure 45mm LPS1270 234, or Tecdur DC49GG GridGlass 49mm (LPS1270 246 SR6 glass as door vision panel in Stafford Bridge Wilton & Halton), or Surelock McGill S-11750-5200 vision panel (steel bolt through cassette with mesh) (Robust UK Tuff-Dor4); or ExcluGlass4 (Sunray Excludor4 door vision panel), or Sentinel4 vision panel (Ultrasecure door)
EN1627 RC5	Sicurtec Attack RC5 45mm / RC5 Panic 50mm poly glass
USA Navy very high threat 7.62mm rifle 150 grain lead core FMJ	Poly glass of: 52mm layup of 46mm 7-ply laminated annealed glass of 3mm + 12mm + 12mm +12mm + 6mm polycarbonate, or 52mm layup of 47mm 9-ply laminated glass of 3mm heat strengthened glass + 44mm laminated annealed glass of 3mm + 12mm + 12mm + 12mm + 5mm polycarbonate
NIJ 0108.01 III	Ionomer glass 37.9mm (Annealed 2.5mm + Trosifol poly 0.76mm + annealed 8mm + Trosifol 0.76mm + annealed 10mm + Trosifol 0.76mm + annealed 8mm + Sentryglas poly 5mm + annealed 2.5mm + Trosifol Ultraclear 1.52mm + Trosifol Spallshield 0.18mm); Secur-Tem+Poly SPN316 poly glass 39mm
EN1036 BR6 NS	Saint Gobain Stadip Protect HS / Vetrotech Vetrogard laminated glass 73mm (+P8B); Poly glass: HardGlass Guardian poly glass 39mm, or Vetrotech Polygard Pro poly glass 38mm (+ SG2 NS + P8B), or Silatech ShooteQ BR6 NS 41/90 poly glass 42mm (P7B), or Sicurtec Bullet 36mm, or Hammerglass poly glass 39mm; Ionomer glass 39.5mm (annealed 8mm + Trosifol 0.76mm + annealed 8mm + Trosifol 0.76mm + annealed 8mm + 0.76mm Trosifol + annealed 6mm + Sentryglas 5mm + annealed 2.5mm + Trosifol Ultraclear 1.52mm + Trosifol Spallshield CPET 0.18mm / SGX can be substituted in same thicknesses)
UL752 8	Secur-Tem+Poly SP820 poly glass 50mm
NIJ IV	Secur-Tem+Poly SPN420 poly glass 50mm
ST-STD.01.01 FEBR 15 rifle	Ionomer glass 45.34mm + 6mm air gap with Sentryglas ionomer interlayers (tempered 12mm + 4.57mm + tempered 12mm + 6mm air gap + heat strengthened 6mm + 4.57mm + heat strengthened 6mm + 0.2mm film)
EN1627 RC6	Sicurtec Attack RC6 50mm / Sicurtec Rc6 Panic 71mm poly glass
Druganov NS	Silatech ShooteQ Druganov 60/117 poly glass 60mm
EN1063 BR7 S	Laminated glass: Vetrotech Vetrogard laminated glass 85mm, or Saint Gobain Stadip Protect HS 83mm
7.62 AP	Lam poly 150mm
AK47 AP	Silatech ShooteQ AK47-NS 62/141 poly glass 62mm
EN1063 BR7 NS	Laminated glass: Vetrotech Vetrogard laminated glass 81mm, or Saint Gobain Stadip Protect HS 87mm laminated glass, or Vetrotech Vetrogard BR7-NS P8B laminated glass 89mm; Poly glass: Silatech ShooteQ BR7 NS 63/127 poly glass 63mm (NATO Stanag 4569 2 + P8B), or Sicurtec Bullet 67mm
UL752 4	Ionomer glass 36.4mm: Annealed 8mm + Trosifol 0.76mm + Annealed 10mm + Trosifol 0.76mm + Annealed 8mm + Sentryglas 5 mm + Annealed 3mm + Trosifol Ultraclear 0.76mm + Trosifol Spallshield CPET 0.18 mm, Secur-Tem+Poly SP412 poly glass 31mm; Laminated glass 54mm
AK47 AP Gost2014 NS	Silatech ShooteQ Gost2014-4NS 67/133 poly glass 67mm
EN1627 RC6 Panic	Sicurtec Attack poly glass 71mm RC6 Panic
Wall to SR5	Bastion Wall with Protean; Remtech Modusec (also CPNI option); 12” grouted hollow concrete blocks reinforced with no6 rebar on 8” centres (c. SR5, c. D20)
LPS1175 SR5, glazing LPS1270 XX5	Poly glass: Tecdur poly glass 46mm LPS1270 235, or ESG Secure poly glass 57mm LPS1270 235 & EN1063 BR5 (or 60mm); R&D Sheet Metal SecureView5 vision panel; ExcluGlass5 (Sunray Excludor5 vision panel)
Wall to SR6	R&S Sheetmetal Security Evo VI; Burton Orthrus (SR6 also achieves F10 & G5)
LPS1175 SR6, glazing to LPS1270 XX6	ExcluClass6 (Sunray Exludor6 door vision panel)
Druganov AP	Silatech Gost2014-5NS 95/203 poly glass 95mm
FFV 7.62 x 51 VMS HK (armour piercing tungsten carbide core)	Sicurtec Bullet 135mm poly glass
LPS1175 SR6, glazing LPS1270 XX6	Tecdur Gridglass poly glass 51mm LPS1270 246
LPS1175 SR7, glazing LPS1270 XX7	No products (would need to stop 54V tools, petrol grinder & chainsaw, 4t jack, scaffold pole, hoollie bar, enforcer)
LPS1175 SR8, glazing LPS1270 XX8	No products (would need to stop arcair, oxyacetylene, concrete chainsaw, rescue chainsaw, ring saw, diamond core, 5t rabbit jack)

Frames

• Remember that domestic windows are specified with an expansion gap of 4-28mm (typically 10mm) so there is always room to jemmy between window and wall through insulation or sealant. Sealed units then have a further edge clearance gap between glass and frame (the frame gives the ‘tight size’ of the pane) including the bottom one containing spacers such as setting blocks on which the unit sits, and location blocks top and sides; there is also a face clearance gap between glass and rebate containing sealant or gasket. Typical clearances are 3mm for face between glass and stop, 6mm for edge between glass edge and frame, and 25mm bite – being the extent of the stop across glass (edge engagement), meaning a typical stop (rebate or rabbet) depth of 31mm.
• Security window frames should be fitted to BS5357.
• Frames should be bolted with embedded anchors during wall construction, or retrofitted with taper bolts, as sleeved anchors can be too thin.
• Under attack, proprietary fixing bolt or ‘anchor’ failure can be by sheer (snapping), pull-out (levering straight out, bringing a 45-55 degree tension cone of wall with it, by prying the in-plane, especially from the hardest concrete which expansion bolts cannot embed into), pry-out (pulling out whilst bending), edge failure (too near the edge, typically edge closer than 12 bolt diameters). Pull-out is a risk especially if the anchor is thick and short, but thin and long ends up with a snapped bolt so thick and long is what you want. Conventional anchors, such as bent bars and plate anchors, can be stronger as they tie into the wall, but have to be built into the wall during construction. Brick is much worse than concrete against bolt failure. Wedge anchors are rarely a good idea for brick as they concentrate pressure too much for brick’s low tensile strength, so sleeve anchors work best. You need to know what will happen to your wall if someone hammers it via the fixing bolts.

Glazing:

Burglary standards

• The UK insurance standard for security glazing is LPS 1270, which focuses on manual attack, although police claim is it not necessary for homes. It aims to limit holes to 8mm x 25mm rectangle for a tool, or 60mm circle for a hand or stealing keys, or 225mm x 400mm for entry to match LPS1175 for the rest of the building fabric. The number suffixes are the old LPS1175 SR ratings for each size hole. Whilst many security glasses can stop somebody climbing through after using the higher toolsets, few can stop a hole big enough to put a hand through or fish for keys, and hardly any can stop a hole big enough to slip a wire through to manipulate catches. Because LPS1175 is aimed at stopping bodily entry, the last of the three digit certification code should match the frame it goes into, so for example if your wall and window frame are SR3 then you need glass ending in a 3. LPS glass rated 012, for example, allows a wire through in less than a minute with merely toolset A (like a screwdriver), but stops a hand with toolset A like SR1 for 1 minute (as SR1 stops toolset A for 1 minute), and stops bodily entry even with toolset B like SR2 (like a hammer) for 3 minutes (as SR2 stops toolset B for 3 minutes).
• The EU standard EN356 only tests a mechanical axe and does not consider hand holes. So LPS 1270 is effectively the next level up from EN356 as it considers risk of manipulation through tool holes and real attack methods combining a range of tools.
• SBD also approve security glazing, including for terror, such suppliers include Cardea with their SBD rated Hammerglass UV stabilised polycarbonate which can give P8B with 8 or 10mm, and P7B with 6mm; SBD rate it for terror in P8B or BR1 upwards.
• Government sets a confidential standard for counter terror standard for

Products

• In terms of layups, glazing is either ‘monolithic’ with one pane or ‘multi-ply with several panes.
  • The only monolithic security glazing is polycarbonate which is for low grade threats.
  • Plies include interlayers like PVB foil, so, for example, 7.5mm anti bandit laminated glass with 2 x 3mm annealed glass panes sandwiching a 1.5mm PVB interlayer is three ply.
• Glazing can then be either single or multiple.
  • A single glazed unit (SGU) is simply slotted into a frame exposed to the room or outside on both sides.
  • A multiple glazed unit (MGU) (such as a double glazed unit) has several pieces of glazing with all sides hermetically sealed except the outermost ones.
  • You often want the expensive glazing on the inside so that weather and vandalism hit a sacrificial pane.
• Pretty much all security glazing is effectively polymer glazing as it includes polymer, either as layers (polycarbonate) or interlayers (EVA, PVB or ionomer (or resin)).
  • Layers are either glass or polycarbonate (or rarely an acrylic core).
  • Combinations of layers and interlayers are either:
    • laminated glass (usually annealed or strengthened glass glued to PVB interlayers),
    • ionomer glass (laminated glass glass using thick ionomer interlayers such as Sentryglas or even extruded ionomer layers instead of polycarbonate),
    • polycarbonate glass or glass clad polycarbonate (polycarbonate core and/or protected face, glass attack face, glued with interlayers including PVB for glass),
    • (monolithic) polycarbonate for low grade threats, or
    • laminated polycarbonate (for higher grade threats).
• Glazing against manual attack is often labelled ‘forced entry’ or ‘FE’, glazing against bullets ‘bullet resistant’ or ‘BR’ and glazing which does both something like ‘BR/FE’, but confusingly a similar label ‘FEBR’ is used for forced entry glazing that passes even after being shot first – it does not promise to stop bullets. The UK has one FEBR standard, CPNI MTAS BFES, part of the government marauding terror attack standard. You thus need to check what standards glazing has certified to as some have separate ratings for forced entry and ballistic, and some for ‘enhanced forced entry’ where the piece was softened up with bullets before manual attack. For example, inch thick laminated polycarbonate will stop a .357 magnum or the full sequence of manual attack to grave V of the USA standard ASTM F1233 but maybe neither if attacked by both. There is no standard that tests such a scenario, only some standards that test forced entry after shooting, so you actually need three standards if you want that something approaching that level reassurance: ballistic, forced entry and enhanced forced entry – but still it does not certify that a bullet will not get through after manual attack, only that a manual attack will not get through after a bullet.
• Roughly speaking, as threat severity rises, materials switch from polycarbonate through laminated annealed glass through laminated polycarbonate through glass clad polycarbonate to ionomer glass. Glass is used to blunt high velocity bullets, for stiffness against blasts and to absorb energy from short manual attacks. Polycarbonate is used to reduce glass cracking and delaminating in high energy attacks, but can only stop high velocity bullets alone in impractical thicknesses, needs protecting by glass against severe manual attack and needs laminating against severe attacks to stop cracks propagating through its thickness. Ionomer is used instead of polycarbonate for its partial self healing ability.
• There are only two players in the UK LPS 1270 market:
  • ESG
    • Their UK insurance rated product is ESG Secure, rated SR1 to SR5, which can come ballistic equivalent to BR2-BR7.
    • They say their 11.3mm P6B product is SR1 rated. Their 13mm laminated glass to P8B only gets you SR1 under LPS1270 and weighs 37kg/m2, with no rating against hand holes, yet their video claims one of their 13mm P8B products suggests its stops a sledgehammer or axe. This is the way marketing is done in the industry as punters want to see sledgehammers not lump hammers, and normal people do not sit still long enough to watch a five minute BRE test anyway. It does delay a sledgehammer, just not for as long as it delays a lump hammer, and not for a certified time. Also, it is a cheaper glass-only product to a nasty continental standard.
    • Fortunately they have stronger polycarbonate glass. More relevant to homeowners, their SR3 glass is 22.5mm thick and weighs 41kg/m2, but, despite being BR2 ballistic equivalent, only buys a minute against a hand hole and does not stop a hole being made for a wire, although you can solve that if upgrading to the 46kg/m2 26.5mm. Just to manage expectations, even the 60mm can be penetrated by toolset B in 3 minutes and can only delay a hand hole with toolset C for 5 minutes to be certain, and it weighs 100kg/m2. If you do not like hand holes then your choices are do not have a window or imbed a metal grid into the glass. To be fair, reinforced concrete behaves similarly, allowing penetration by tools and arms long before rebar is cut to allow bodily entry.
    • Their thicknesses for various ratings changed in their 2021 flyer, the author understands due to clients demanding larger panes than used in LPS1270 tests, eg fully glazed doors.
    • The author has been in touch with ESG, who responded at speed and at length, so can confirm they can work with homeowners on a supply glazing only basis, or can put you in touch with manufacturers who might be able to make up a door or window with or without an LPS1175 rating including their glazing, as they are committed to the high net worth residential market. So, whether you want to zombieproof your house against looters or build a Bond villain lair they should be able to help. They supply military vehicle vision panels so can probably handle your house.
  • Hamilton Erskine
    • They supply through their subsidiary Saint-Gobain’s distribution brand Glassolutions.
    • Their two product lines are essentially Stadip laminated glass, and Tecdur which includes a choice of low ratings laminated glass and high ratings resin bonded polycarbonate glass (with GridGlass option against cutting and ballistic and blast options), rated from EN356 P1A to P8B and SR1-SR6, although they have also said only up to SR4 or SR5. 
    • GlassSolutions’ Stadip Protect laminated glass uses 0.78mm PVB interlayers, is only safety glass and comes in thicknesses 4.4-13.5mm and is not LPS rated. It can come in ‘HS’ handgun & rifle, ‘HC’ shotgun and ‘FS’ combined ballistic and forced entry, and ‘BS’ blast versions. Oddly they claim that their P6B is equivalent to SR1 whilst also saying they need a P8B to hit SR1, and a table in their brochure implies that P7B is SR2 and P8B is SR3 when actually they would need to almost double the thickness to achieve those LPS1175 ratings.
    • Tecdur‘s laminated glass can only take you up to P8B and SR1 despite its 29mm thickness. Their P1A-P5A safety glass is glass-only, with polycarbonate glass coming in from P6B upwards, and both options for P6B up to P8B/LPS1270 001. It can be modified to use their Planidur heat strengthened glass, Securit tempered glass or Securipoint heat soak tested tempered glass.
    • Their Tecdur polycarbonate glass can achieve the same LPS1270 001 (delays bodily entry by toolset A for 1 minute) at 16mm thickness, while 51mm of GridGlass gets you up to a rating of 246 (delays 8mm tool hole by toolset B for 3 minutes, hand hole by toolset D for 10 minutes and bodily entry by toolset E for 10 minutes). Battery tools take several minutes to cut out a square within the metal grid which then slows down bodily entry.
    • Their Tecdur poly glass 20mm SR3 product is probably most relevant, as that is graded to match maximum brickwork strength and should see off a screwdriver for 1 minutes to stop a wire poking through, a hammer for 3 minutes to stop a hand coming through , and an axe for 5 minutes to stop bodily entry.

• Cardea’s Hammerglass silicon oxide-coated polycarbonate is a potential alternative.
  • It is not rated LPS1270 as they see no commercial benefit, but is rated to EN356 P7B (6mm) or P8B (10mm). However, the 10mm and 12mm have effectively been rated rather higher than that via LPS1175 SR2 and SR3 as part of Premier’s glazed doors as a thinner lighter alternative to ESG Secure, eg where chemicals and weather are not big risks.
  • It is available as single, double or triple glazing up to P8B in 6-12mm (sealed units teamed up laminated glass), or as single glazed cassettes with glued glazing and frames coach bolted to existing windows for internal or external use as Windowguard. Insulated units have gaps of 16-24mm to stop internal or protected face glass being broken during the flexing of the attack face Hammerglass. Gaps as thin as 12mm have been known to prevent one pane crashing into the other but for insulation and maximum flex space 20mm-ish is better.
  • They say they can get P4A or P6B with 4mm (4.8kg/m2), P7B with 6mm (7.2kg/m2) or 7mm, and P8B with 8 (9.6kg/m2) or 10mm (12kg/m2). It also comes in ballistic polycarbonate glass in 23mm (54kg/m2) to BR4 NS or 39mm (90kg/m2) to BR6 NS. After being shot it will be dented by bullets and much of the pane will become opaque white in a diameter around the shots. It can get BR1 as a cassette of 12mm plus 4mm sacrificial layer. The 12mm is blast rated to EN13123 EXR2 and they say has been tested against a 1kg 100mm diameter roundnose steel bullet at 450km/h withstanding 7,800J. Hammerglass 6mm in normal window sizes will be at most scuffed by a baseball bat (it broke the bat in one test), marked by a lump hammer and dented by a sledgehammer or axe.
  • It is also available through Premier SSL who tested it to SR2 and SR3 as part of their door range. It stopped someone climbing through even after 5 minutes of drilling a circle of holes, chiselling them together (making ‘lands’) and lump hammering the disc. Premier say their SR2 doors with 10mm can take the shock of an enforcer or battering ram.
  • You will see it vibrate with a sound like a gunshot from the impact (in slow motion it ripples for a tenth of a second), but it won’t crack or cave in with such tools until after a lot of impacts if correctly fixed. In door-size panes, long tools will flex it more than you might want to see, although often it would not be noticed if looking straight on.

Ionomer

• Like polycarbonate, ionoplast is an elastomer, polymer and thermoplastic. It has been used by the military (eg Du Pont’s Surlyn) as a replacement for polycarbonate layers in laminated glass for its partial self healing ability, but the civilian market uses it as an interlayer, invented by DuPont, from the only manufacturer, calling it Sentryglas. Depending on heat, Surlyn snaps back together after penetration by a missile and any remaining hole is partly healed by viscosity, hence it is popular for military fuel tanks

Acrylic

• Acrylic, technically known as polymethyl methacrylate (PMMA), with brandnames of Perspex and Plexigas, is four times stronger than glass (and more than twice as light) but over twenty times weaker than polycarbonate. It is sometimes used as a thicker, cheaper, clearer, UV stable, more polishable, easier-to-glue substitute for polycarbonate in low rated ballistic glazing, either monolithic or as a core to polycarbonate. It can be laminated with a glue of the same refractive index, which is how they make giant aquariums. It was invented in 1928 and marketed in 1933. When it fails, big lumps shatter off like annealed glass, so it is not much use for multiple ballistic strikes, but 32mm of it can stop a 9mm at UL752 1 and there are manufacturers around who can cast it thick enough for level 2 or laminate it for level 3. It can be improved against impact with comonomers or plasticiser, eg Perspex T3. Apart from brittleness it is way more flammable than polycarbonate and vulnerable to chemicals, so is it little more than filler to be protected by other materials in low threat panes – where heavy tools, guns, chemicals or torches are not expected, so not much use after SHTF.
• Applicable standards are as for polycarbonate.
• Acrylic rated products are hard to come by. If you used it then it would be sourced by a manufacturer, probably as a laminate core.

Polycarbonate

Tips

• The original brandnames for polycarbonate were Makralon in Germany and Lexan in USA.
• Polycarbonate weighs 1.3kg/m2 per mm thickness, compared to glass which weighs 2.6kg/m2per mm thickness. Polycarbonate can cost about 10 times as much as annealed glass, but could thus save on special hinges and frames. A 1” thick pane for a window size about 18” square would weigh about a stone, so is manageable. Polycarbonate tolerates squashing and stretching (snaps at twice its original length) so is great against brute force and blunt instruments, but has its limits especially as it is plyable and can be formed into shapes at room temperature. It can be harmlessly bent and is even used for domes and curves as an architectural product; the typical security thicknesses of 6-12mm can be bent into a 7-8’ circle without affecting strength.
• 0.76mm polycarbonate backing to 3mm annealed glass lets it pass P1A. Sandia say that up to 25mm thicknesses are easy to cut with power tools. Polycarbonate is better than laminated glass at stopping chisels under flame (a USA prison break test), and monolithic has been tested at 24% longer lasting than laminated for that purpose, while dividing up polycarbonate in glass clad polycarbonate instead of a monolithic core reduces penetration time by about a third, and using thicker interlayers for lam poly helps but ultimately increases thickness compared to just using more poly. Doubling thickness from 1/8″ to 1/4″ can up to treble number of blows required and trebling thickness to 3/8″ provides a delay of 7-9 times longer. Polycarbonate is no use on its own thinner than 12mm, especially against axes. 0.5” can last up to 2 minutes against an axe. Thicker versions can last up to 10 minutes.
• Polycarbonate benefits from being protected by laminated glass with an air gap from heat attack like propane torches or from heat differentials from weather – even just 6mm lam glass is enough to make a big difference. ‘Protecting’ polycarbonate from chisels with glass simply increases thickness slightly and weight a lot. It can struggle with spalling against shotguns. It also needs the protection of glass if sophisticated criminals are expected as it can be destroyed by chemicals, although polycarbonate laminate has more chance against chemicals as the interlayer may not be susceptible. If it is cordless rotary cutters you are worried about then you need some glass layers, including on the attack face, so polycarbonate is not ideal for high end jewellers where expensive tools are likely, although ballistic Hammerglass could work as it is glass clad. Polycarbonate is hard to burn and self extinguishes, although melts at 147c. It becomes brittle at -135c. Polycarbonate breathes gas and absorbs water slowly and becomes brittle at 25kGy radiation so might not be ideal for NBC applications. Polycarbonate can craze under temperature differences between sides of pane. It expands ten times more than glass in heat so eventually delaminates as the interlayer wears out from constant shear.
• There is some evidence that if using polycarbonate interlayers instead of PVB interlayers you are better off using larger panes, presumably as polycarbonate is so much stiffer than PVB and channels more energy into frames and glass rather than safely flexing. In practice it makes glass about 2.5 times stiffer than PVB. This could allow you to reduce rebate depth. It also helps delay delamination from weathering and is less yellow.
• Polycarbonate’s main vulnerabilities are to heat and weathering. For humid or salty air a coating should be considered for polycarbonate. For polycarbonate thicknesses over 5/8” exposed to sub zero temperature a urethane interlayer should be considered. Its water vapour permeability means sealed units need condensation drains. Holes for fixings should be drilled in controlled conditions to reduce heat stress and must be 1.5 times the fixing diameter and need rubber washers. Expansion gaps should be 3mm/m.
• Polycarbonate is eaten by chloroform  or methylene chloride. It can also be depolymerised by alkalines like low molecular weight organic solvents such as acetone. It is vulnerable to solvolysis and hydrolysis. It shrugs off 10% sulphuric acid as it is OK with diluted acids. But it does not like salt water (especially around fixings), concentrated acids, ethylene glycol monomethyl ether, ammonia, hot petrol, carbon tetrachloride, sunscreen, dioxane, butyl acetate, dibutyl phthalate, diethyl ether, dioctyl phthalate, ethylamine, methanol, potassium hydroxide, caustic soda, styrene, tetrachloroethylene, hot ammonium nitrate, hot soda, dimethyl formamide, the DETA in decontaminant DS2, aldehydes, ethers, ketones (crystallisation), esters, aromatic hydrocarbons (stress crack), halogenated hydrocarbons, perchlorinated hydrocarbons, alkalines (especially hot), alkali salts, amines (surface crystallisation) and high ozone concentrations. Some attacks would take several days while bending the pane. Hammerglass say their coating stops acetone yet slightly suspiciously recommend it for burning off scratches. Care must be taken to avoid gaskets and sealants containing chemicals like PCV – which polycarbonate cannot tolerate.
• Polycarbonate is made using chemical weapons like phosgene but the finished product is food grade and used in medicine.
• Polycarbonate is used for riot shields, and entry level stab vests like PPSS 5mm KR1 against knives but not ice picks.

Standards

• The old British Standards BS5051 (ballistic) and BS5544 (anti bandit) remain relevant to plastic security glazing.
  • BS5051 requires no spall and 3 shots in a 100mm triangle from a gun or 1 shot from a shotgun at 3m for handguns and 10m for long guns, with ratings from G0 for 9mm to R2 for 7.62mm rifle and S86 for shotgun 12 bore lead slug.
  • BS5544 drops a 2kg 82mm diameter steel ball 5 times from 3m and once from 9m within a 125mm circle.

Products

• Cardea‘s Hammerglass silicon oxide-coated polycarbonate is an alternative.
  • It is available as single, double or triple glazing up to P8B in 6-12mm (sealed units combined with laminated glass), or as single glazed cassettes with glued glazing and frames coach bolted to existing windows for internal or external use branded Add-ons or Windowguard, with RC2 option, in 6, 8, 10 & 12 thicknesses). Hammerglass polycarbonate window shields are available from SecurityGrillsDirect PremierSSL and WindowSafetySecurity, in security thicknesses of 4-10mm. Insulated units have gaps of 16-24mm to stop internal or protected face glass being broken during the flexing of the attack face. Single panes are available in 6, 8, 10, 12, 15, 17 & 20mm thicknesses. They also sell insulated windows.
  • Hammerglass’ light transmission is 88% at 1% and UV protection is 99.96%. It can absorb up to 50% of solar IR radiation.
  • They say they can get P4A or P6B with 4mm (4.8kg/m2), P7B with 6mm (7.2kg/m2) or 7mm, and P8B with 8 (9.6kg/m2) or 10mm (12kg/m2). It is also available through Premier SSL who tested it to SR3 as part of a door. It stopped someone climbing through even after 5 minutes of drilling a circle of holes, chiselling them together and lump hammering the disc. Premier say their SR2 doors with 10mm can take the shock of an enforcer or battering ram. Hammerglass 6mm in normal window sizes will be at most marked by a baseball bat, will be marked by a lump hammer and will be dented by a sledgehammer or axe, and you will see it vibrate with a sound like a gunshot from the impact (in slow motion it ripples for a tenth of a second), but it won’t crack or cave in with such tools if correctly fixed. In door-size panes, long tools will flex it more than you might want to see, although often it would not be noticed if looking straight on.
  • It also comes as polycarbonate glass in 23mm (54kg/m2) to BR4 NS or 39mm (90kg/m2) to BR6 NS ballistic. After being shot it will be dented by bullets and much of the pane will become opaque white in a diameter around the shots. It can get BR1 as a cassette of 12mm plus 4mm sacrificial layer.
  • The 12mm is blast rated to EN13123 EXR2 and they claim has been tested against a 1kg 100mm wide round nose steel bullet at 450kmh withstanding some 7,800J.

Laminated glass

Tips

• Glass types: Security glass means laminated glass, with or without polymers layers. Manufacturers typically make glass from 2-19mm thick, or sometimes even 25mm or 30mm, with strengthened and tempered glass in more restricted thicknesses.
  • Annealed glass is weak as it smashes easily with nothing to hold it together, and, although it may deter some burglars due to the danger and noise and often gets DNA conviction from blood, it leaves shards all over the room or even you. Annealed glass is 30% as strong as steel and is hard, takes massive compression and resists stretching, unfortunately it lacks toughness, is way more brittle and is elastic so does not deform to absorb strain, so shatters while steel is ductile so would have allowed itself to be moulded around a sledgehammer but not let it through. Annealed glass cracks in a spiders web of concentric circles (which start on the attack side) some distance from the impact with radiating lines (which are the only type of crack on the protected face and slower if more numerous in laminated glass) starting on the protected side, and which start before the circles in petals of blades and branch out into tributaries and go sideways too) extending up to it forming ‘pizza slices’ and some continuing past it leaving a few large shards that can give a modicum of stiffness to the interlayer, then some of the energy goes into exploding the shards sideways in the plane of the pane towards the frame. This is what happens to a bullet if it hits something harder.
  • Toughened or tempered glass is five times stronger (120MPa to EN121540-1).
    • Tempered glass is heated then rapidly cooled. It can be bought as laminated glass up to 5″ thick but after 2.5″ thick it tends to look unacceptable.
    • It will not stop a sharp impact with enough energy. It is only designed to break safely, not to not break. It it cracks into tiny pieces at about 0.2 milliseconds per foot (1,458m/s) by cracking into trapezoid-ish ‘dice’ in narrower radials than annealed glass, longer in the direction of travel than they are wide, radiating out in a circle from impact to edges, at the speed of sounds in glass, then splitting into long thin clumps also radiating out from impact which explode along the plane of the pane, even upwards. This happens faster than a bullet which is why glass helps soak up so much energy by doing a lot of cracking while the missile is still indenting the attack face.
    • Pros
      • It can be used to protect laminated glass from accidents, or for blast glazing or for vandal resistance, but would then still immediately weaken the whole pane as soon as it cracks.
    • Cons
      • Even when it breaks it is allowed to have some long shards which have been known to kill kids falling into it.
      • It is worse than annealed glass as attackers may know it falls into safer and quieter pieces with one shove after cracking.
      • Toughened or strengthened glass can be a delamination risk as the rollers it cools on in the factory cause droops.
  • Heat strengthened glass is halfway between annealed and tempered glass in strength. It can be used in ballistic or forced entry laminated glass.
    • Pros: It breaks like annealed glass so holds up interlayers better, as long as compressive strength is under about 30MPa.
    • Cons: Strengthened glass costs 20-350% more than annealed glass depending on thickness.
  • Chemically strengthened glass is dipped in an alkali bath and stores energy in the top 0.3mm so breaks into big shards.
    • Pros: Its large shards when broken help hold up an interlayer.
    • Cons: The shallowness of chemicals can be penetrated by defects during manufacture which eventually explode, although it can be specified to be treated deeper.
  • Wired glass would only be used for fire and ballistic purposes to protect polycarbonate.
  • Safety films will stop shards flying but will still cave in under a hammer and can be pushed in with a buttstock within a minute after shooting it.
• Interlayer types:
  • Interlayers are simultaneously resins, polymers and thermoplastics. Choices are PVB foil, EVA foil, ionomer foil or injecting resin (cast in place). Interlayer manufacturers include Dupont, Kuraray, Solutia and Huakai. Interlayers are theoretically vulnerable to fail due to brittleness when they become ‘glassy’ when frozen, although glass is an insulator so protects it. And when heated they go through stages of being leathery, rubbery and eventually liquid.
  • PVB:
    • Polyvinyl butyral (PVB) is a polyacetal of condensation of polyvinyl alcohol and butyraldehyde.
    • Its free hyroxyl groups bond nicely to silicon atoms of glass.
    • The interlayer in laminated glass is normally PVB, in multiples of 0.38mm such as 0.76mm and 1.52mm, which is autoclaved to dry and glue it.
    • PVB was originally used with 0.76mm foils in car windscreens, and still is, as it soft enough for pedestrian heads.
    • You might be able to find the aircraft grade of PVB which is twice as stiff as architectural PVB. Blast or ballistic glass tends to use 1.52mm PVB interlayer, with ballistic using more glass layers and more total thickness.
    • PVB initially stretches less under stress then much more under strain until finally it snaps.
  • Ionomer:
    • Sentryglas (‘SG’/’SGP) is the monopoly brand of ionoplast polymer interlayer made of ethylene or methacrylic colpolymer and a dash of metal salt, connecting ionic groups to a carbon chain backbone.
    • Ionomer quickly stress then stress drops a little and it strains, becoming less ductile.
    • If using Sentryglass as layers they are typically 1.52mm for blast or ballistic, so about 10% of the layup, but this has to increase to 35% for P8B manual attack, and at P8B allows manufacturers to reduce glass plys from five to three and interlayers from four to two. However, Sentryglas increases thickness compared to using PVB in P1A-P5A safety glass as otherwise its stiffness would let the steel ball in the test shatter it. It only reduces total thickness at P6B upwards and for blast and ballistic.
    • To get BR4 NS or NIJ IIIA you could use a 21mm layup of 14.5mm total glass thickness (69% of layup), 5.9mm Sentryglas and 1.52mm PVB, so to stop the bullet needs the layup to be about 29% Sentryglas. As that layup includes a 5mm Sentryglass layer it should also deal with manual attack, despite it being slightly glass-heavy for manual attack. The similar Ul752 3 to also stop a .44 Magnum needs 19mm glass so is 77% glass. To get up to BR6 NS nearly doubles the total thickness but uses an 85% glass layup so you are not massively better off against manual attack.
    • The notable performance benefit from Sentryglas comes at 6.84mm where it takes a ASTM F1233 glass up a grade from 1 to 2, whereas in thinner versions it does not beat PVB in that test; in 5-aa1 tests it takes more of a beating than PVB in every thickness, soaking up kicks at 1.52mm, 2 mins of tools at 2.28mm, 3.5 mins of tools or 6 mins of sledgehammer at 4.56mm, and 6.84mm adds the benefit of no hole in an attack that would make a small hole in the 4.56mm.
  • Urethane interlayer costs nearly three times as much as PVB.
  • Polycarbonate is a glazing material in its own right but can be used in thin panes as an interlayer in the sense that it holds broken glass via interlayers, although normally as thick as glass so it is more of a layer than interlayer. It mostly it provides the toughness (and stiffness compared to thin soft interlayers) while glass provides the hardness (and stiffness and thermal and chemical resistance). It is more for blast and forced entry than ballistic as it needs ridiculous thicknesses for high energy rounds.
    • Pros
      • Tough so hard to crack, and stiff until stretches and even then it is hard to snap.
    • Cons
      • If used on the attack face it only has a lifespan against weathering of 10 years even if specially coated.
      • It costs about ten times the price of tempered glass. Polycarbonate costs about 10-60 times as much as annealed glass depending on thickness.
      • It suffers major edge reaction and shear in stiff frames.
• History: Laminated glass was invented in 1902 and technology has not come very far since; all that has happened is the original cellulose interlayer has been replaced by cellulose acetate in 1933 and then PVB in 1939, now with alternatives such as EVA, resin or ionoplast allowing choice of stiffness, yellowness, noise insulation and weathering.
• Cons:
  • Ultimately glass is a terrible product for security and is really just to keep rain out and let light in.
  • Glass suffers from brittleness which is only well cured by tempering, which makes it worse by turning it into tiny fragments when it breaks, which pulls down interlayers like a wet towel and allows in pointed or edged weapons like bullets or axes through cracks to interlayers, which in turn cut or rip off from interlayer. This lets it fend off one hit from maybe even heavy tools (so could work against vandalism or smash and grab), but it does like repeated hits (like a mob WROL burglary by starving neighbours).
  • Laminated glass’s main vulnerability is freezing, as fire extinguishers etc can be used to stress them before ramming.
  • Laminated glazing of any material is vulnerable to delamination in humidity, especially with most laminated glass as PVB is hydroscopic, so bathrooms may need special treatment and it always needs to breath around edges.
  • Glass displays a range of variation of 150% in maximum stress at failure due to each pane having different surface flaws.
  • Even the thinnest laminated glass stays in place against an axe, but what sales videos don’t show is that it can be pushed in within seconds; hence the market for polycarbonate glass. This is the conundrum of laminated glass: the glass needs the PVB to hold it together and the PVB needs the glass to hold it up.
  • Sandia say 10mm laminated glass only buys 1.5 minutes against hand tools before a crawl hole is made. 13mm laminated glass lasts about 1.5 minutes against hand tools. Even BR4 ballistic 32mm laminated glass will let someone point a gun through a hole after about 30s of sledgehammer. Perhaps the best video on laminated glass is from ESG (who mostly make poly glass), showing how bricks bounce off even just 11.5mm anti bandit glass, but, once attacked with tools, cave in within seconds, eg 11.5mm allows a hand hole with a lump hammer in 4s, 13.5mm allows a hand hole with a sledgehammer in 5s and, interestingly, with a lighter lump hammer in less time – 3s – once cracked. It shows how thick toughened glass buys extra seconds but soon reveals the vulnerable PVB layer as glass fragments pour off. 30mm P8B laminated glass is seen stopping a hand hole for 3s against a sledgehammer. They then show off their 13mm P8B ESC Secure poly glass seeing off an axe and sledgehammer for over a minute with no penetration.
• Pros:
  • A Rene Turck video shows how decent thickness laminated glass lasts eight times longer than a brick wall against a sledgehammer.
  • Glass is cheaper than polycarbonate and so also cheaper than polycarbonate glass.
  • Glass is harder against scratches by vandals and weather, and protects against chemical and thermal attack.
  • Glass is stiffer than polymer so is stronger until broken; it can survive severe attack, but only if very thick, and its chances are much better against one blow – like a blast, one stray bullet or someone accidentally falling against it. It would be ideal if you fear a nuke in a neighbouring town but due to your armed response and sightlines you do not fear shooters or burglars, especially if you can tolerate thick frames as you have thick walls and thick skin when it comes to aesthetics.

Standards

• EN12543: Laminated glass should be made to BS EN ISO 12543:2011 and BS EN 14449:2005.
• EN12600: Safety glazing should be to BS EN 12600:2002, although that is too thin to be security glazing.
• BS5544: Even though a brick would crack the top layer then bounce off, a hammer can put a hole in old school BS5544 ‘anti bandit’ 11.3mm laminated glass with 2 blows. It is much the same with a sledgehammer against 13.5mm, and even 23mm laminated glass can be even worse, maybe if it is only engineered towards axes. 11.5mm anti bandit laminated glass (2 x 5mm annealed + 1.5 PVB) is often found in PAS24 or LPS2081 products and can be punched out of its rebate by a sledgehammer in seconds.
• EN356:
  • Protection against manual attack can be to BS EN 356:2000 but the author cautions that it is usually only glorified safety glass.
  • The European standard does not categorise according to tools, time or hole size, and even at its higher grades for security (P6B-P8B) it just says whether an axe made a 40cm square hole.
  • All that EN356 tests at lower grades for safety (P1A-P5A) is dropping a 4kg steel ball from a few metres 3 times (9 times for P5A) with 62-370 joules energy for grades P1A to P5A; at P6B-P8B grade it tests number of 2kg axe blows to cut out a 40cm square (after softening up with a 2kg lump hammer).
  • 6.8mm laminated glass – which is the building regs and SBD specification and gives you P2A under EN356 – is all but useless against burglars.
  • GGF advice is that typical laminated glass thicknesses to achieve EN356 are P1A = 6.8mm, P2A = 8.8mm, P3A = 9.1mm, P4A = 9.5mm, P5A = 10.3mm, P6B = 15.3mm, P7B = 22.3mm and P8B = 26.7mm.
  • Laminated glass to EN356 P8B against axes can, according to one manufacturer, be 16.5mm thick weighing 30kg/m2, while other products need thicknesses of 23mm, 27mm or 36mm.
• LPS1270: You are recommended to go for LPS1270.
  • LPS1270 is the glazing equivalent of LPS1270 for barriers if you want to choose your own glazing.
  • LPS1175 barriers like windows come tested with scheduled glazing as an overall SR rating (now given as separate tool and time score) in which case you do not need a separate LPS1270 glazing rating.
  • The downside of LPS1270 is the duopoly between ESG and Saint Gobain. But then again LPS1175 windows are even more of a monopoly as the only residential window manufacturer is Hampton and the only secondary glazing manufacturer is Selectaglaze. If looks do not matter than you can of course go for the much wider range of institutional products and swap in LPS1270 glazing or keep what they come with under LPS1175.

Products

• Security laminated glass manufacturers include:
  • Saint Gobain
    • Vetrotech, distributed through their brand GlassSolutions
      • Vetrogard Attack to P6B-P8B,
      • Vetrogard Bullet to BR1-BR7 & SG1-2 & AK47 NS & Kalachnikov,
      • Vetrogard Pro range combines ballistic & manual attack to P8B,
      • Vetrogard Blast to ER1-ER4,
    • Tecdur EN356 version rated P1A-P5A (everything above that they add polycarbonate),
  • Pilkington (Optilam anti bandit to P2A-P8B or spalling ballistic to BR2 S-BR7 S), and
  • Global Security Glazing (Secur-Tem & Secur-Lite anti bandit to UL972).
• As Pilkington do not have no-spall ballistic, or forced entry glass beyond anti bandit levels with only EN356, they are not hugely relevant to armed residential burglary scenarios. Global only have anti bandit to a similarly low USA standard, so are also not a key contender. That leaves you with Tecdur, or Vetrogard Attack or Pro who can combine ballistic with anti bandit to EN356, but unfortunately neither to LPS1270 in laminated glass only products so are not ideal either. Whilst these EN256 ratings would be enough for the EU’s EN1627 RC1-4 grades on the continent, this effectively means that for serious manual attack to LPS1270 you must look to poly glass, which basically means Saint Gobain’s poly glass version of Tecdur, or ESC Secure.

Polycarbonate glass

Tips

• Polycarbonate glass or glass clad polycarbonate is laminated glass including layers of 1-12mm polycarbonate stuck to glass by polyether urethane or potentially any other resin. Beware unbalanced polycarbonate glass with most of the polycarbonate on one side of the cross section, as it can cause delamination. Normally manufacturers try to pack the polycarbonate towards the middle, with or without glass in between, with glass on the surfaces.
• Some ballistic polycarbonate glass has a toughened low-spall protected face glass surface. Alternatively for ballistic units manufacturers put most of the glass on the threat face to absorb impact and most of the polycarbonate on the protected side to stop spall.
• Pros:
  • It can comes out at as little as half the thickness of laminated glass.
  • Because non splinter versions of laminated glass are easily 50% thicker, incorporating polycarbonate to keep the thickness down can make sense.
  • Poly glass is more for forced entry and ballistic use than blast, as against blast you want inertia and stiffness and do not need much protection against multiple impacts.
• Cons:
  • As poly expands in heat eight times more than glass it usually needs at least 1.2mm urethane interlayer to allow the shear; sometimes 1.5mm PVB is used, doubtless as it is three times cheaper than urethane. With poly cores thicker than 16mm there is so much insulation that temperature differentials could degrade the pane, so you would use urethane interlayer for sub zero weather and air gap for anything below minus 15 degrees C. You choose either cheaper poly glass now that needs replacing sooner, or pay for urethane and air gap now and it lasts longer.
  • Beware toughened glass attack faces as these can crumble quickly with multiple shots.
  • Poly does not like extreme aspect ratios or delamination eventually occurs.
• A high security alternative to polycarbonate glass is ionomer glass or glass clad ionomer. That type of laminated glass has an ionomer core soft enough to start to glue up saws. It is restricted to the military, so all you can buy as Joe Public is almost certainly laminated glass using a stiffer ionomer called Sentryglas as interlayers. Your challenge the would be finding it in the UK and getting a security rating on it.
• Research has found good results from using polyurethane instead of polycarbonate in single clad glass or on its own, with 20mm layup stopping a 9mm, 23mm stopping a .44 Magnum and 38mm (18mm glass + 20mm polyurethane) stopping a 7.62 ball round. Versions with high strain rates and thus high damping factor were found to stretch backwards like a net and then spring the bullet back at the shooter, with some of the rest of the energy turned to heat by raising the temperature of the bulge by about 14 degrees celsius, whereas polycarbonate tends to eat the bullet. The product needs to be manufactured with transition temperature just below the operating climate – not easy with the weather outside and room temperature outside or in mild but variable climates like Europe and USA between the arctic and tropics, although it can be manufactured to cope with a range of 45K. This is the same material sprayed on unreinforced walls against blast and manual attack. Another successful experiment embedded glass balls in polyurethane, but this is hard to commercialise as the polyurethane needs to have low viscosity, low shrinkage, long setting time and near identical optical properties to glass By using glass ceramics like spinel instead of glass high threat weapons can be stopped.

Standards

• Standards for polycarbonate glass are as for laminated glass, as it is a type of laminated glass, and is not a pure plastic product so does not come under the old BS5544 – it just uses polymers for some layers as well as all interlayers.

Products

• LPS1175 rated polycarbonate glass on the market includes Tecdur TSG and ESG Secure; in fact it is the only LPS1175 rated glazing.
• Tecdur typically uses a tempered glass clad sandwich of resin-encased polycarbonate, eg for 18mm it is 2 x 6mm tempered glass + 2 x 2mm resin + 2mm poly. The 2mm poly can hold up the exploded tempered glass after the first impact shatters it, but broken tempered glass provides no extra stiffness and provides maximum amount of cracks to exploit through, while the poly replaces the stiffness that would be provided by broken dices of tempered glass under tension on a flexing PVB interlayer. A sophisticated adversary who sees the characteristic tempered break and the glass dice spalling off the protected face yet not collapsing may guess it is Tecdur and start cutting the poly interlayer.
• ESG make poly glass for manual attack or combined ballistic and manual attack to EN356 P8B, or P8B + LPS1270 112-235, or P8B + LPS1270 + EN1063 BR2-5), plus blast upgrade option although most of their products appear to be inherently blast resistant to several grades.
• An EN356 P8B poly glass from Germany claims to stop a car at 30mph:

Laminated polycarbonate

Products

• Laminated polycarbonate is glued with polyurethane. Laminated polycarbonate typically comes with 3mm facings of abrasion resistant polycarbonate protecting a couple of core layers.
• You can buy Lexguard laminated polycarbonate in 18mm, 21mm, 25mm & 32mm thicknesses, all of which are ballistic, which at 32mm thickness will stop a 44 magnum and weighs 38kg/m2, but won’t stop a shotgun; 25mm of it will stop a 357 magnum and an axe, chisel, splitter maul, ram, sledgehammer, propane torch, CO2 extinguisher, petrol or acetone will bounce off, so is great against unarmed but determined burglars. Manual attack versions are available from two ply 9.5mm to four ply 32mm.
• Pros:
  • It is stronger than monolithic polycarbonate as breaks are not so easily transmitted through the thickness of the pane.
• Cons:
  • Polycarbonate can delaminate under temperature differences between the sides of pane.
  • Vulnerable to thermal and chemical attack.
  • Needs massive thicknesses for high energy ballistic.

Blast

Tips

• Windows on exposed facades should be minimised and ideally limited to courtyards or skylights and light pipes used instead.
• Aspect ratio affects displacement in small blasts in rigid frames – in bigger blasts the glass is punched before the frame gets a chance to twist the glass.
• Blast windows should be flush and rigid all the way into the wall.
• Blasts impart energy quickly in the positive impulse, although due to the square law it rapidly and increasingly reduces with distance. Blasts such as gas or nuclear then have a negative impulse, which lasts longer but is weaker and which will try to suck a window out after the positive impulse softened it up, and it sometimes succeeds.
• The job of any blast barrier is to convert kinetic energy into strain energy.
• A blast window is expected to deflect slightly, as even if the glass does not suffer plastic deformation the frame may rotate and laminations may slide across each other.
• Commercial blast ratings are really glass retention ratings used to estimate likelihood of being cut by flying glass in terror attacks. They are nothing to do with stopping blasts or fragments coming in – for that you need custom blast frames and ballistic glazing. The assumption is that eyes can be pierced at 0.06J.mm² and skin at 0.1J/mm². Annealed glass is thought to be dangerous at 5KPa, where as anti bandit glass 7.4mm-11.8mm holds out at 29KPa-55KPa in one test, and in another 8mm anti bandit survived 39KPa-49KPa in one piece, another test saw 17.14mm (8mm + 1.14mm + 8mm layup) survive 1Kg TNT at 5m and 21.14mm (10mm + 1.14mm + 10mm) tore but stayed in the frame against 30Kg TNT at 5m (1,064 KPa).
• Nukes:
  • Nuclear blasts last longer so are a problem even for heavy materials, as inertia is more likely to be overcome. The other problem is that in the UK most home walls would be damaged as most of the population live in or near a structural damage zone (in Japan it was 3 miles for the equivalent of UK brick houses), so there is the question what will your window attach to unless you reinforce the wall? And the roof if you want shelter. There is also the danger that the home is softened up by oscillations from ground shock before the air slap arrives to finish it off.
  • For Japan nuke window effects see USAEC Window & glass hazards under wartime conditions & recommended protective measures.
    • Glass broke in an area 16 times bigger than the structural damage zone.
    • Keep panes under three square feet.
    • Avoid splitting windows into panes with thin cross members. These can be stuck on to one pane decoratively instead.
    • If you anticipate a nuke, open inward opening windows to equalise pressure and keep the glass safe ready to close later against fallout in case you still have a roof by then. Most outward openers, except those on the leeward side, would slam shut and likely smash the glass. Closed windows will not save you from a thermal pulse, for that need special blinds hanging loose so they do not tear. M profile black plastic blind slats worked well in stopping shards.
    • Annealed glass only 6mm thick resists 2.5PSI which – would start demolishing a brick house. 5mm annealed glass handles 1.4PSI which about as as high as you can go before risking structural failure strength of a brick house. Annealed glass in small blasts shatters into large shards and drops under the window but in big blasts shatters into smaller shards projected through the house at anything up to 45 degree angles from the blast.
    • 1/4″ acrylic is only slightly stronger than 1/4″ tempered glass.
  • For test results see USAEC Effect of Atomic Weapons on Glazing & Window Construction.
    • The usual consideration that rigid frames increase stress in glass and increase cracks gives way to needing rigid frames if you mainly fear living too close to ground zero, as otherwise a nuke will twist frames which breaks the glass.
    • 1/8″ acrylic survived unscathed where 1/4″ wired glass was blown in.
    • It was suggested that reinforced venetian blinds could protect from flying glass 3 miles from the blast and aluminium ones could protect from the heat pulse 2 miles away.
    • Wire netting with 1/4″ 20-23 gauge mesh stapled and clamped stopped all but the tiniest shards.
    • Glass blew in, even on the leeward side, but fragments also flew past the building as the blast was faster than gravity, and windward window shards were sucked out by the negative phase.
  • As an idea how involving a long pulse from a small nuke on the UK would be, we have real world data from England in the form of Buncefield petrol depot disaster. An area the size of a city suffered at least sporadic minor damage with windows coming in up to 4 miles away, and an area the size of a county was panicked, by a 2m tall vapour cloud 0.12 Km in area which ignited, generating 200KPa, equivalent to ‘only’ 30t (estimated range from 7.5-50) TNT, still pushing about 5KPa one mile away. Incidentally, in terms of state help through the fire brigade, they were blocked by debris, ran out of foam and had to get water from 2km away, which may be a clue whether they will save you after a whole town or city is nuked, when water mains are fractured and your county is riddled with radiation.

Components

Film, curtains & catch cables

• Windows can be strengthened against blasts through mitigation to reduce injuries with
  • anti shatter film and sometimes also bomb blast net curtains (both for annealed glass windows that cannot be replaced), or
  • laminated glass not bonded to the frame, or
  • can be protected through bonded glazing and special frames to hold the glazing in place.
• Film:
  • Film is certified to EN12600:2002. It should have a tensile strength of at least 172 MPa and peel strength of at least 930N/m. Film is usually made of polyester such as BOPET (bi-axially oriented polyethylene terephthalate), around 0.1-0.6mm thick and sometimes laminated with glue, glued to the glass with about a 2mm gap round the edge (daylight application) allowing it to blow out in one safer piece. Stronger application methods are wet glazing – where the film is masticked (eg Dow Corning 995 structural silicon) and mechanical fixing – where it is screwed down with beads. It is better at holding fragments together than holding panes in frames. The minimum useful thickness is thought to be 0.18mm.
  • According to research, 0.18mm daylight film makes barely any difference. Wet glazing as as good as laminated glass the same thickness as the monolith it is applied to. Mechanically attached film is much better than laminated glass as thick as the equivalent monolith at higher loads.
  • Film can avoid injuries from flying glass at scaled distance of up to about 13m/kg^0.33, so still only half the strength of a standard wooden door.
  • For annealed panes up to 3m² and up to 6mm thick, above the 11th floor use film for anything worse than a car bomb and for 6th-11th floors you use film (plus nets for anything worse than a car bomb), whilst for any bombs for 1st-5th floor you use film and nets; use at least EN12600 2B2 100 micron film. For annealed panes over 3m² or over 6mm thick, above the 11th floor use 2B2 film for anything worse than a car bomb, for 6th-11th floors use nets and 2B2 film (plus nets for anything worse than a car bomb), for 1st-5th floors use nets and 1B1 175 micron film. The thinnest rated blast film is 4 mil and the thickest 25 mils, but normally you need at least 7 mil. Avoid US DHS guidance on films as they have decimal points in the wrong place and muddle thousands of an inch with millimetres.
  • Film and curtains are to roughly halve the standoff distance for shards.
  • Blast film and even thin laminated glass, even in double glazed units, can be rolled down under the glass’ own weight after attack by axe or crowbar, so whilst they may stop car bombs at a distance spraying shards onto inhabitants they are not for manual attack.
  • Film is generally only for blasts up to 70kPa peak pressure and 700kPa-msec impulse.
  • A test found that film can nearly treble blast resistance of annealed glass from 1.5kg.cm² to 4.2kg/cm², which is not saying much.
  • In the Bishopsgate blast, filmed glass was found to have flopped into rooms near the window or even been caught by venetian blinds.
  • Pros:
    • Cheaper than new glazing
    • Invisible
  • Cons:
    • Film only lasts about 10 years before UV light weakens it too much.
    • No use for manual attack other than a tiny bit of spall protection.
• Curtains
  • Blast curtains are polyester to BS4407, with burst strength of 550kN/m2 to BS4768, with 50g/m2 mass to BS2471, as little as 0.5mm thick with thread to BS6157 CPFT70-120 (continuous polyester filament ticket, fire resistant to BS5867 Part type C, with a 400g/m lead hem and double width.
  • Curtains have an overhang of one to two metres usually about half the window height, which is fixed at the bottom or has a weighted hem that concertinas into a retaining box or dynamic tension retainer.
  • They catch shards but still billow three feet on impact.
  • They are idea for small wooden panes.
  • Rails are 16mm polished aluminium with thimble brackets and must be 10cm from the glass and reveal fixed or 10cm wider than the window each side if face fixed.
  • Only really for annealed glass in listed buildings or unbonded laminated glass, which may not be a good idea for manual attack
  • Cons:
    • Need big rooms where you can sit well away.
    • Need frequent cleaning as the are white.
    • Have a tell-tale ‘this is a government building’ look.
  • Pros:
    • Obscuration during daylight.
    • Cheaper than new windows.
• Catch cables are typically 6mm with shock absorbers, or bars, and are used to catch blast glazing in the event it stays in one piece but flies inwards. Ideally you use plastic-deformable attachments to extend survival beyond the cable’s limit.
  • Cons:
    • Looks conspicuous.
    • These are known to sometimes simply chop each glass missile into two glass missiles unless used with laminated glass.

Glazing

• Double glazing: Bear in mind that a blast can deflect the outer pane to impact the inner pane in the centre, and even if the sealed unit is gas-filled a big blast could make the outer pane hit the inner one before such an adiabatic gas spring kicks in.
• Monolithic glass:
  • A single pane a glass of any type is ill advised against blast as firstly it needs to be thick and heavy as it cannot be allowed to crack like laminated glass can, secondly if it ever does break the whole lot turns into sharp missiles towards inhabitants and thirdly it has to be so stiff it may well tear the frame or wall as the wall opening area of blast is concentrated into at best its perimeter of fixing.
  • Doubling thickness increases bending stiffness by eight times. The same is assumed for laminates for impacts.
• Laminated glass
  • How laminated glass is supposed to work in a blast is the glass bends, the inner pane cracks under tension after about 2ms, the outer pane cracks, the interlayer stretches elastically and then plastically and then tears due to sharp glass or strain rate. In reality it is not always retained in the frame so blows out in one piece.
  • At 90kPA (18t TNT at 15m) a test was conducted on 7.5mm anti bandit laminated glass, with 3mm + 1.52mm + 3mm layup, found glass absorbs most energy for the first 5ms before almost completely relaxing while cracks compress against each other, then having started absorbing at 2ms the interlayer absorbs much more and most energy for 7.5ms while the pane reaches maximum deflection at 111mm at 15ms and holds it in plastic deformation after a slight rebound and never recovered, cracks continue during deflection, and simultaneously the rubber sealant gradually absorbs up to 2.5 times as much energy as the glass did for 7.5ms then mostly relaxes, and after 12ms glass and silicon stop doing most of the work and the interlayer takes over. At 20kPa (18t TNT at 25m) the test found glass did most of the work as it was never badly damaged so the interlayer only had to stretch for the small deflection of 34mm at 12ms and bounce back, which it did further then the original deflection. Another test with 10kg TNT at 9m found a 7.52mm window blow out at 50ms whereas a 13.52mm window reached maximum deflection at 21ms. Another test measured glass starting to move at 23ms, accelerating at 6km/s2 and peaking at 24m/s in 6ms, with the centre accelerated at 3-6km/s² peaking at 17-31m/s.
  • Increasing tensile strength of glass mainly only helps reduce deflection in the strongest blasts.
  • You probably want to minimise deflection in security windows even though that is not the most efficient way to stop a blast, as you need the window to not have any tears that intruders can exploit. This tends to mean less and stiffer sealant, thicker glass, thicker and stiffer interlayer and beefier frames than pure blast windows.
  • Failures modes of laminated glass in blast, putting to one side failures of wall, fixings or frame which will not happen if specified properly, include interlayer tearing, interlayer delamination, lateral glass cracks (like sliding into two thinner panes) and sealant cohesive tear. Theoretically a sealant could suffer adhesive failure coming off the glass or frame.
  • The Instanbul HSBC blast was an example of all laminated glass windows being blown in yet not seriously injuring anyone.
  • A shock tube test (see Johns) found glass windows explodes into a hemispherical cloud with larger shards at the front.
  • Load bearing increase slightly with increased layers for a given total thickness as interlayers share the bending and membrane stress (see Parratt).
  • Mitigation options:
    • If windows cannot be completely replaced then one mitigation option other than film or curtains is to replace glazing with laminated glass not bonded to the frame with at least 0.78mm interlayer and overall 6.8mm thick.
    • Ideally you add protections such as secondary blast glazing, replacement blast glazing or you bond blast glazing to the existing frame.
    • Beware that going beyond filing existing glass to replace it with laminated glass, for example, will probably exceed the strength of the frames, so the cost efficient solutions are filming existing glass or replacing with complete blast windows (see research).
  • Blast frames:
    • If you buy blast frames you typically glaze with 7.5mm laminated glass inside, and in double glazing add 6.8mm laminated glass outside if you just want to reduce the risk of flying shards. 6.8mm can be used for double glazing if that is all the unit can accommodate for low risk situations, but normally the minimum glass thickness for the inside pane is 7.5mm in 35mm rebates and ideally glued.
    • Laminated blast glass goes on the inside face of any multiple glazed unit.
    • It has been posited that chamfering rebates would reduce stress by allowing rotation. This makes room for crowbars, but this author suggests that a workaround could be that the rebates are changed from loose siliconed ones to clamped tapes ones swinging on hinges up to 30 degrees released by a blast valve or simultaneous force around the frame to make it hard for intruders to simulate a blast. The reason to consider it is that edge stress creates more small cracks, which weaken laminated glass against manual attack, so you should avoid it by tolerating ‘elastic’ frames that are still strong enough to resist being kicked in by a mob. It is not ideal as you may need catcher cables to hold the pane in against intruders, if not the blast.
    • Support reaction is the energy dumped into the frame:
      • It peaks at about 7ms.
      • It lasts longer the bigger the blast.
      • It only increases with a bigger blast if the glazing does not tear.
      • Its tendency to quickly fall over time disappears if high tensile strength glass is used against big blasts.
      • Likewise support reaction oscillations are bigger and take longer to tail off with thicker glass.
      • Increasing interlayer PVB thickness slightly increases support reaction but nowhere near linearly.
      • In a big enough blast stiff enough interlayer slightly increases support reaction.
      • Increasing sealant depth in a big enough blast roughly linearly increases support reaction between 10-20mm sealant depth. Increasing sealant depth 100% from 10mm to 20mm could increase support reaction about 150% depending on blast size.
      • Reducing sealant thickness from 5mm to 4mm (20%) increased support reaction 17% in a bigger blast, and in a smaller blast by 8%, so is key in bigger blasts.
      • Increasing sealant Youngs modulus slightly increases support reaction or more significantly in bigger blasts with very stiff sealant, eg 48% increase in Youngs modulus gave 42% increase in support reaction in a test at 90kPa.
  • Fixing:
    • Laminated blast glass is fixed by either bolting, structural silicone or gasket.
    • The interlayers need to be specified differently according to fixing type.
    • Use 35mm deep rebates for gaskets or ideally PDMS silicon or polysulphide sealant with its high shear strength, or 30mm deep rebates for clamps.
    • Sealant:
      • As little as 12mm delamination causes laminated glass to probably burst out of its rebates in its rated blast. You can mitigate against this with wider silicon bite.
      • Sealant should be at least 5mm thick and ideally 6mm thick but ASTM2248-09 calls for total sealant thickness to be between 1 and 2 times total glass thickness. Thickness increase can reduce deflection significantly but only in bigger blasts and the gain is far from linear and it makes no real difference to energy absorption, although upgrading from 4mm to 5mm reduces support reaction.
      • Sealant depth changes make more difference in small blasts, and only after 8ms, but you need about 20mm before you get the benefit of it for any blast strength and before you get a decent increase in energy absorption, and beyond 12.5mm most of the benefit is already gained.
      • Sealant should have 20 PSI tensile strength, hardness of 4-60 IRHD and Youngs modulus of 1.5-3.4 MPa. Increasing Youngs modulus reduces support reaction but only reduces deflection in stronger blasts.
      • Roughly speaking, to avoid dumping too much energy into the frame and thus needing an expensive ugly heavy thick one, go for flexible thick shallow sealant.
      • Laminated glass, if it does exit the frame, tends to pull out at 30 degree angle at a strain of around 20kN/m.
      • It has been posited that chamfering sealant would reduce stress by easing rotation.
  • Thickness:
    • As a rule of thumb in blast calculations, laminated glass is treated as monolithic glass of 75% the total thickness of glass layers, so weaker, but retaining most glass to stop it flying, but this is thought to fall to as low as 50% in hot climates where it acts more like a stacked plate than a monolith.
    • Increasing pane thickness slows it, which helps get transverse waves to the middle by the time deflection peaks, the ratio of glass velocity to transverse wave velocity improving by the square root of the thickness increase, to maximise use of interlayer to or even past tearing strength, and thus avoiding tears at the edges which could let the whole pane fly in, although glass will crack earlier on in deflection compared to thinner panes.
    • Laminated glass about 32mm thick weighing 75kg/m2 to BR4 is the sort of strength that stops blasts to ER4 level; the PVB layer must be at least 1.52mm thick.
    • Glass thickness matters more than interlayer thickness in blasts.
    • For reduced scaled distances below 11m/kg^0.33 laminated glass thickness has to increase more than polycarbonate. At this energy level laminated glass is as strong as polycarbonate for preventing injuries from flying glass, but by 4m/km^0.33 you need 12mm polycarbonate or 14mm laminated glass.
    • For the sort of blasts that a domestic wall can take you will rarely need a blast window beyond what an FEBR ballistic forced entry glass can handle. This can have the advantage of avoiding such thick sealant which a crowbar could exploit, although unfortunately ballistic glazing normally relies on sealant damping too. In fact, ballistic glazing can protect blast glazing’s integrity by preventing it being weakened by a pre-emptive bullet or fragment from a multiple blast, even if you do not fear being shot and do not expect manual attack beyond a typical anti-bandit sort of thickness blast window; the danger is from the protected half’s plys being damaged (41% weaker in 1/4″ laminated glass) as damaged attack face does not weaken against blast (see Reznik 6.5.5).
    • Doubling the thickness of the plate more than doubles its load capacity.
    • Try to specify the thinnest glazing possible with equal thickness plates.
    • Specifying glass layers thicker than 19mm limits suppliers and costs disproportionately more so it becomes cheaper to pay for extra lamination.
    • Laminated glass for blast should always be at least a total glass thickness of 6mm and each pane must be at least 3mm.
    • It has been posited that chamfering glass would reduce stress by allowing rotation.
  • Interlayers
    • PVB:
      • Laminated glass needs medium stiffness family 1 PVB interlayer, such as Everlam Lam54J or Kuraray Trosifol Ultraclear B100 NR.
      • Laminated blast glass usually needs architectural PVB interlayers of at least 1.52mm (sold by Kurary, (Trosifol, the best being Trosifol Clear B100 LR), Everlam (Lam 51H, the best being Everlam 54J), Eastman (Saflex, the best being Solutia RB11) & Sekisui (S-Lec)), although these should be kept cool to avoid delamination.
      • The best PVB interlayers for blast are Everlam 54J and Trosifol Clear B100 LR.
      • The interlayer should be 1.5mm.
      • In a blast, PVB allows the pane to stretch along the edges while the middle stays fairly flat in a pillow shape, with the bend only continuing to the middle in a hill shape caused by transverse waves in stronger blasts travelling along glass at typically 143-193m/s (faster the thicker) depending on thickness before glass breaks and 36-15m/s in stronger blasts after it breaks (slower the thicker); eventually a strong enough blast will then tear the PVB, which happens at about 20cm deflection and between 6ms and 8ms; this classically happens at the top of the corner of the pyramid shape diagonals stretching out to the flat centre, and can reduce strain on sealant thus potentially avoiding the pane blowing in.
      • Thickening the PVB increases tear resistance by avoiding strain concentrating along the edges of the flat top of the cushion-shaped deflection, and lets breakages form as more but thinner cracks in glass, but makes little difference to energy absorption and only reduces deflection a lot in strong blasts, which it does after 8ms, but on balance thicker interlayer protects the interlayer as well as glass. Going too thin risks a tear and the blast entering the room as every crack means a stretch in interlayer which thins it and so pulls it off the glass on both sides, whilst going too thick risks losing the benefit of deflection in keeping energy away from what you probably want to be slim frames. Once aspect ration exceeds 1:2 the deflection tends to lose its flat top and become a long pyramid with a ridge instead.
      • With 10mm cracks for example, energy to failure for 0.38mm hovers around 6 kJ/m2 whereas 0.78mm takes about 14 kJ/m2, 1.52mm takes around 40kJ/m2 and 2.28mm takes some 45 kJ/m2. Except at high strain rates, there is not much to be gained here from 2.28mm PVB, and 0.38mm is ruled out, 0.78mm shows more than linear gains and quadrupling the 0.38mm to 1.52mm gives you six times the ultimate strength. As the 0.78mm would still fail as it cannot delaminate faster than it snaps at ligaments holding across cracks, the 1.52mm is the best option, although it as it relies on delamination to avoid tearing is risks flinging off shards of glass so a spall solution is needed, eg XO Armour film.
      • Another test found increasing PVB thickness from 1.52mm to 2.28mm perversely increased maximum deflection from 275mm to 280mm allowing the pane to be partially pulled out albeit with no tears compared to the torn PVB in the retained thinner pane. In a square window the deflection strain peaks in roughly a circle in small blasts and trends towards a square in bigger blasts.
      • One method of mechanical fixing is to additionally clamp an excess flap of interlayer.
      • Stiffer interlayer with higher Youngs modulus only makes much difference in deflection (which protects glass and sealant slightly) and then only for stronger blasts, which it does after 9ms.
      • Manufacturers and installers need to take care with humidity, cleaning fluids and silicon contact with PVB, ideally have panes custom made.
      • Adding laminations slows glass fragments but increases cost, although some of that can be offset by using thinner plates.
    • Sentryglas:
      • Kurary’s Sentryglas ionomer polycarbonate (SGP) interlayer is normally too stiff and expensive, and is more for unsupported edges in safety applications, although a security engineer could design a window with a strong enough frame, otherwise it is too strong for blasts, ie lacks ductility, so could rip the frame out instead of flexing.
    • EVA: Ethylene-vinyl acetate (EVA), such as Bridgestone’s Evasafe, is to be avoided as although it resists delamination and survive moisture it tears easily.
    • Poured resin (cast in place), such as Kommerling Kodigard, is another interlayer to avoid as it is weak, vulnerable to UV delamination and only used as a last resort for shaped products.
    • TPU: It is bad news for polyurethane (TPU), such as Polymar, too as it is not only ruinously expensive but weak, although sometimes necessary for ballistic glass to stretch with the plastic laminates.
    • EVA, iononomer and TPU are better at resisting delamination but only suited to non blast applications.
• Annealed glass as a monolithic pane is ruled out as it typically shatters at about 0.2PSI, and one test found it a 4mm 0.89m² pane survives up to 12KPa. Another problem is you never know when it will shatter as tests have found one annealed glass snaps at 30MPa while another snaps at 120MPa. However, when laminated its low breaking strength is not a problem as stronger glass contributes next to nothing against deflection (see Morison para 9.5.4). Annealed glass is about 20% weaker against a 1s pulse than a 10ms pulse, and can be estimated to be some 15% weaker against a nuke of say a 0.5s pulse with the same overpressure than a short sharp 20ms shock of TNT. It is a problem because glass tolerates either significant peak overpressure and impulse much better than both at once. Impulse tends to end while the window is still reacting whereas overpressures tend to end after the window has reacted.
• Wired glass is half the strength of unwired annealed glass and expels fragments so is equally useless.
• Tempered glass:
  • Thermally tempered glass (TTG) is sometimes used for blast glazing; for example, about 3.5” of it laminated as three plys of ¾” backed by two plys of 5/8” in a 5’ square window could stop a half ton bomb at 60 feet, and two layers of 1/8” of it in a one foot square window could stop it at 200 feet.
  • In the 1986 Lovelace test comparing results with ratings laminated thermally tempered glass was found to survive a blast that was supposed to have a 99% failure rate.
  • Despite its risks it does get used as an outside pane in blast double glazing, and military still specify it.
  • It can also be specified for low risk blast use as an overall 6mm laminate.
  • The extra tensile strength can reduce the total glass thickness required.
  • Cons
    • This flies inwards as clumps in a blast so is not as good at chopping flesh but creates dangerous missiles, often in the shape of ‘ice daggers’.
    • Tempered glass is worth avoiding even if laminated as it can explode due to nickel sulphide inclusions and can panic people by sounding like a gun. The workaround is to pay the manufacturer to soak test it at over 250c to BS14179.
    • Tempered blast glass is unlikely to be of interest to preppers as it leaves manual attack and ballistic threats unaddressed, whereas there are manual attack and ballistic specifications using other materials that are either certified for blast or we know are equivalent from their layup.
• Chemically strengthened
  • Chemically strengthened glass is only OK for blast if precompressed deeper than 0.3mm.
  • The lithium coated version is three times stronger than tempered glass yet breaks into big shards which help hold up interlayers.
• Polycarbonate glass:
  • Polycarbonate glass should be blast rated according to either its glass or polycarbonate but not both.
  • Lam poly is treated as monolithic if glued with urethane interlayer.
• Polycarbonate
  • Pros
    • Polycarbonate was tested by US DoS in 1988 and found to easily exceed its ratings, similar findings emerged at Fort Polk in 1991. In test to failure it was screws that failed in aluminium frame, allowing the window to be sucked backwards in negative phase. Depending on size of pane and blast 6mm can be expected to deflect 10cm by 10ms and doubling thickness to 12mm only reduces deflection by a quarter. In the same test the 6mm ended up bent by about 18mm and the 12mm not at all. 32mm polycarbonate can easily survive 50PSI without even stretching, while 19mm polycarbonate easily survives 15PSI.
  • Cons
    • In comparison 7mm laminated glass only deflected 3cm against 6mm poly’s 10cm.
    • Polycarbonate is harder than glass to keep in the frame in a blast, even if laminated with glass. It needs a bite of 150% its thickness as per ASTM2248-09.

Frames

• Ideally blast frames are two-piece: an outer frame embedded in a concrete pour, and an inner frame bolted to that in the set wall. Anchor bolts should be to 900 MPa yield and 1,240 MPa tensile, minimum 10mm thick on maximum 30cm centres, minimum 10cm deep and minimum 75mm from edges. Fixings may need to be specified to cope with rebound. Frames should be engineered to 167% of design threat stress, fasteners tying inner to outer frame and outer frame headed studs to 200%, and to expansion bolts to 400%.
• Blast frames should be double the strength of glazing to ensure the whole thing does not fly into occupants and to give glass time to break.
• Another standard is to specify glazing that fails in 75% of attacks to make it likely that if it comes in it does not bring the frame with it.
• Frames must be as strong as the glazing otherwise even if they do not burst out they may distort and so rip the glazing; this why aluminium can be a problem, eg in a test with 1/4″ tempered monolithic glass, aluminium frames nearly wiped out tempered glass’s extra strength (8.27 kPa) due to distortion, even though the glass could have handled more, and rigid wooden frames did nearly four times better (30.3 kPa); reinforced aluminium frames (with screwed beading) could only handle 17.9 kPa. Annealed glass 1/4″ thick resisted 5.38kPa in rigid wooden frames. Annealed glass 3/8″ thick handled up to 10.8 kPa in a rigid wooden frame. Tempered glass 3/8″ thick handled 30.3 kPa in a rigid wooden frame.
• Frames for laminated glass are allowed to move up to the lesser of 3mm or 1/264^th of span, and 1% for polycarbonate.
• Frames should be rated for stress at 1.65 of yield stress and fixings at twice yield stress.
• Beading must not rotate more than 0.5 degree for single plate glass, 1 degree for laminated glass or 2 degrees for polycarbonate. Even steel frames rotate slightly, which helps take energy out the glass.
• If the window is allowed to fail after a blast then it can be rated at 67% of static frame design load for the negative pressure phase.
• Aluminium frames can be strong enough up to 5PSI but only if reinforced with steel. To push the envelope with aluminium you could try using smaller window sizes.
• Walls need to be stronger than the window to avoid masonry flying in or even collapsing, but that is difficult once windows are an inch thick and tying to beams may simply damage the beams, instead they need a thick wall or to be tied to floors.
• Some blasts will spall even concrete walls behind fixings but sometimes the bolts remain firm nonetheless.
• If you make your home bomb proof then think about how you will stand out like a sore thumb after the blast in a terror attack or war. Not many criminals have access to explosives, but they have eyes.
• Using gaskets or sealants to reduce stress on frames leaves them open to manual attack, so such multifunction windows need overengineering. Wet sealing can help retain glazing in a blast.
• Aluminium or steel blast frames become necessary in addition to blast glazing once you want to exceed (go below) a scaled distance of 11m/kg^0.33.
• Fixings rely on either friction, adhesion or bearing and bonding. Friction fixings include expansion anchors.
• Anchors should vary in length to avoid perimeter shear. The longer the anchor the less the stress on the masonry.
• Anchors must be extra strong if teamed with ballistic glass in concrete as most energy will be dumped into them through stiff glazing.
• Anchors experience bending moment and shear force until glass breaks then this continues with the addition of axial tension. The anchor tries to act as a cantilever (see Jacques & Saatcioglu).
• Research suggests that equally spacing bolts ignores how energy is dumped in the wall – you actually need more bolts towards the middle of long spans and fewer bolts, if any, in corners. The more rigid the frame the more uniform the energy send to the wall, so only an infinitely rigid frame needs uniform distribution of anchorage, thick aluminium and thin steel frames tend towards a trapezoid distribution not needing corner bolts, and thin aluminium frames tend towards a sinusoidal distribution not only not needing corner bolts but needing more bolts in the middles of spans and fewer near ends.
• Short height walls may need to increase effective mass to help hold anchors, using vertical stitching on cavity walls or post tensioned masonry anchors, especially if using ballistic glazing.
• Diamond drills should ideally be used to fit anchors to avoid fractures that are more likely with the energy dumped by carbon tipped drills. Holes must be dust-free with room for expansion but not so little so as to stress the wall.
• The US Air Force Research Laboratory patented damping chamber blast window.

Standards

• Blast glazing standards are:
  • ISO16933, which uses real explosives in an arena test on a sample 80cm x 100cm. This gives vehicle bomb ratings from EXV45 up to EXV10 with hazard rating suffix at rated metres distance from 100t TNT with 30-800kPa mean peak & 180-1,600kPa-ms mean impulse, or SB ratings 1-7 for satchel bombs from 70 to 2,800 kPa & 150 to 1,500 mean impulse from 3 to 20 kg TNT at 3 to 9m standoffs. There is no EN standard for open arena so the ISO standard is used because some applications need reassurance against negative pressure after the initial positive pressure above ambient.
  • EN13541 EPR1 to EPR4 for shock tube from 0.5-2.0 bar peak pressure & 3.7-22 bar-ms positive specific impulse against laminated glass. EN13541 tests a sample 3’x3’8” to see if it can take overpressure for 20ms of 5-250kPA. EN13123 covers shock tube and range tests for doors, windows and shutters and EN13124 covers the test method for EN13123.
  • ISO16934 is roughly equivalent but additionally tests hazard to occupants based on damage to glass rated from A = No break to F = High hazard. Apart from ER30 only having to last for 15ms it also tests overpressure for 20ms in a range of 30-200kPA. Ratings are thus from ER30 to ER200 with a suffix for hazard grade A-H. It is deemed blast resistant at grade C = Minimal hazard, and higher. At grades D-E (low to very low hazard) it can be sold as ‘hazard reduction’.
• The standards are for TNT IEDs, not gas or petrochemicals or ammonium nitrate fuel oil (ANFOs) or nukes.
• GGF say blast laminated glass typically gives ER1 spall with 10mm, ER1 no spall with 18mm, ER2 spall with 18mm, ER2 no spall with 26mm, ER3 spall with 31mm, ER3 no spall with 39mm, ER4 spall with 27mm,and ER4 no spall with 33mm.
• The USA DoD navy security glazing handbook specification for blast glazing is:
  • For low threat (blast from attack on neighbour) use 6mm laminated thermally tempered glass.
  • For high threat use blast glazing standards.
• The minimum protection against blast is usually seen as 6mm polycarbonate to at least keep glass shards off occupants. However, a mere 3mm of polycarbonate in an 18” square window could see off a 50lb bomb at 200 feet, or in a one foot square window a 220lb bomb at that distance or a 500lb bomb at 300 feet.
• It is normal to accept that 10% of windows will shed fragments reaching ten feet inside at two feet above floor level, and even the highest standard is still only for fragments to go no further than a metre.
• Your specification depends on charge, elevation, setback and offset. Typical laminated glass thicknesses are 6-84mm of strengthened glass plus interlayers or 6-83mm polycarbonate.
• Pane size increase reduces the blast rating. For example, a 25mm layup of 12mm + 0.78mm + 12mm would give give ER4NS at 70cmx70cm, but falls to ER3NS at 80cmx80cm, ER2NS at 100cmx100cm, ER1NS at 120cmx120cm and unrated at 190cmx190cm.

Products

• ESG claim that all their ESG Secure 1270 and EN1063 poly glass thicknesses are blast resistant to ISO16933 and their LPS1270 223 32mm stays in place against a 100kg blast 10m away. Curiously they publish no details of this.
• Saint Gobain make:
  • Vetrotech Vetrogard Blast laminated glass:
    • ER1 S 10mm
    • ER2 S 18mm
    • ER3 S 31mm
    • ER4 S 27mm
    • ER1 NS 18mm
    • ER2 NS 26mm
    • ER4 NS 33mm
  • The same group, Hamilton Erskine, also make Tecdur Blast Glass poly glass.
• Selectaglaze offer security secondary glazing against burglary, blast and bullets, although they can only achieve SR3 or bullet resistance with fixed demountable units. You could accept an SR2 rating that opens and back it up with a grille inside or shutter outside. All their windows are blast resistant to at least EXV45 with 6.8mm glazing, some to EXV33, most are EXV33 or EXV25 with thicker glazing, EXV25 needing 9.5-11.5mm, and their S55 DFL fixed panels (if with 15mm glazing) and S50 casement can go up to ISO1933 EXV15, and other openers to EXV19 or EXV25, using 1.5mm PVB interlayer.
• Blast windows are available from Schuco (AWS 90 XR) to 169kPa, and Saelzer (Securon) with RC4, FB4 and blast to 100kg TNT giving 0.87 bar.

Ballistic:

Tips

• The first rule of ballistic protection is ‘you cannot kill what you cannot see’ (usually), so you should obscure all windows with curtains, blinds or film. Beware mirror film only works in daylight.

• Ideally avoid windows if you want a ballistic facade, but if you must have them they should be recessed, narrow, and oblique to the perimeter or at least six feet above ground. Rooflights are to be avoided ideally but must be obscured.

• To resist bullets, windows need ballistic blinds, shutters or glazing.
• Frames may need a higher rating than the glazing if your threat weapons have high energy density, which generally means high speed narrow bullets from rifles, as pressure on materials like steel tends to drill straight lines so might punch through whereas on laminated glass or poly glass it is slowed down by ripples of cracking, tearing and bending.
• Stops or beading should be 5mm thick steel profiles. Frames should be 6mm thick steel profiles.
• Tempered glass is cheap, but a no-no for ballistic glazing as it shatters so small that it stops visibility for defenders, adds so little stiffness to interlayers (in fact it tries to fold them) and dramatically increases the chance the next shot hits a crack.
• Interlayers in ballistic laminated glass perform the roles of holding up broken glass to absorb energy by being crushed and letting that glass move backwards slightly. In fact the PVB lets the glass vibrate like a speaker cone’s excursion, initially stretching then snapping back. In contrast polycarbonate is pushed back and wobbles.
• Some ballistic glass puts a low spall layer on the protected face using thin strengthened glass.
• Some ballistic poly glass only uses one poly ply which is on the protected face partly for spall.
• Ballistic glazing is not expected to work within an inch of the edge so the rebate must be reinforced as an extension of a ballistic frame.

UK ballistic risk profile

• In Britain the main ballistic risk from armed criminals is handguns (c. 40%), so you might think that is what you would specify for, rather than thick, heavy, expensive rifle protection (c. 1%), although shotguns are a real risk at c. 9%. However, the twist is that according to licensing there are 3.5 shotguns for every other firearm legally held, and post-SHTF we can expect law abiding citizens to break out shotguns to feed their family, so shotguns could easily become the main risk once the rule of law disappears. There is also the factor that half of gun crime is in the three biggest cities so outside those there is even less reason to prepare for hanguns and instead to expect shotguns and rifles. What you need to know is what shotguns (and cartridges) and what handguns? We know that 99% of licences shotguns are section 2, so hold at most two cartridges, hence a marauder attack is not the main risk, but a shooter could casually keep reloading until they run out of ammo if staked outside your home. We also know that most non-shotgun firearms in the UK are rifles, one for every three shotguns, and that you probably will not protect against them as your wall would need reinforcing and your pocket deepening. We further know that there is only one handgun per ten shotguns, so although they are the criminal’s favourite they are not what is likely coming for you from random hungry citizens. It is estimated there are over three million guns held by civilians in the UK and that government has one gun per five civilian guns.

• Were someone to target your stash they could snipe with a rifle for days until their ammo runs out which would need ruinously thick heavy expensive glass. Machine guns are not stoppable with ballistic glazing, so instead you would eliminate windows or if the only threat is from a long standoff you could protect them with a screen such as a reinforced concrete wall. You probably want to specify for a compromise of protection against the most likely shotguns (SG1-SG2) and handguns from 9mm Luger up to .44 magnum (BR2-BR4), and maybe common low power rifles firing lead round nose (BR1), without exceeding the protection of the surrounding walls, whilst accepting that rifles would get through, but hoping that no guns will get burglars through the glass and few will make big enough holes to intimidate you through. The most common products are rated BR4 which would stop virtually all handguns and low power rifles and low power shotguns; unfortunately they are at least 24mm thick and at that thinness cost a fortune in poly glass. Sadly, if you save money by going for the thinner 17mm BR3 glass poly which can fit it more frames, whilst it will stop low power rifles and any handguns up to a .357 magnum, it will not stop any shotgun slug, but you could decide to gamble that looters will only come at you with buckshot. What you save on the ballistic windows downgrade you can spend on guns!

• In England & Wales as at 2020 79% of firearms attacks cause minor injuries and only 2% kill, but after SHTF there are no hospitals so you don’t want wounds. Only a quarter of firearms offences cause injury. The main risk is intimidation as you need to stop robbers blackmailing you into opening the front door or letting them walk out of with your stuff. Normally we could say the chance of being killed in an armed burglary is about 0.5% but after SHTF robbers may care less about you and getting caught and more about getting your stuff; likewise you will be more willing to fight for your stuff. We could also normally say the chance of being injured in an armed crime is about 23%; this is a very significant risk which you cannot afford to crystallise with no trauma wards available, and a risk that will only skyrocket after SHTF. We also know that if you were hospitalised by a firearm the average stay is nine days with a 30% chance of going in ICU and many needing thoracotomies or laparotomies and emergency medicine consultants, so these are not first aid incidents you can shrug off with a copy of ‘Where there is no doctor’. A shot anywhere other than the arm commonly becomes a medical crisis. Also consider that low UK peacetime firearm death rates are due to junk guns and low energy weapons like cheap handguns; after SHTF we can expect rifles and shotguns being deployed by hungry owners or stolen by looters.

• Like stopping vehicles, stopping bullets is about mass x velocity squared, so heavy slugs are nasty but high speed rifles are worse. As you cannot usually create enough standoff or barrier in a domestic plot to restrict speed or size of bullet you just have to buy what you can afford for the likely risks, bearing in mind how close a shooter can get and how many shots they can get off. In a SHTF scenario this might be point blank and more shots than the rating of 3 or closer together than the ballistic rating’s 12cm spacing. So thicker is not just better but probably essential. With 18mm polycarbonate glass you could stop a drug dealer’s 9mm luger, while with 26mm you could stop a 44 magnum, but to stop a few blasts from a shotgun will need at least 31mm. Above about 20mm you rapidly run out of frames on the market that will accommodate the thickness, let alone the weight.

• Typically ballistic glazing uses laminated glass to slow and blunt the bullet, backed by a polycarbonate spall layer to catch it and stop fragments of bullets or glass. Usually you would expect six layers and every extra layer to stop an extra hit. For example, to stop a rifle you typically need 2” of laminated glass, whereas you can save about 0.5” by replacing some glass with polycarbonate. A thin pane on the attack face helps as ‘disruptor’ by blunting, with inner panes soaking up energy as ‘absorbor’ by Hertzian cone plug.
• Glass blunts the bullet during the ‘dwell’ period, plastic deforming the round, mushrooming mild steel cores, eroding hardened cores (taking the tip off) or shattering the most brittle hard cores, and then the bullet is forced to push a plug of crushed glass through subsequent layers by shear, especially in thin glass. Glass’s Poisson ratio in hard materials like glass helps create a cone shaped Hertzian crack which absorbs energy, and ideally is retained by a spall layer. So if using glass it is better to use a thin sacrificial attack face for blunting protecting a thicker pane to be further crushed. The number of radial cracks depends on the size of hoop stress. Unfortunately cracks do not absorb much energy.
• Spalling occurs due to reflected tensile stress being released from the free surface of the protected face.
• Chemically strengthened glass is coated with potassion ions to fill ‘Griffith flaws’ that can spread cracks (and which are guilty of reducing glass strength by 210 times compared to silica atom strength), leaving it slightly harder but crucially about 20 times stronger against cracking. The other type of strengthened glass is heat strengthened glass which is heated then rapidly cooled and so although stronger than annealed glass breaks in big pieces like it thus reducing the collapse of laminate seen with tempered glass. Its strength has to be at least 70Mpa to EN1863-1.
• Strengthened glass is used as an attack face in some ballistic and blast glazing. Because glass always has flaws it is always so weak in tensile strength that it never gets a chance to break due to compression, which would not be easy anyway as glass is more than twice as hard as aluminium and 70% as hard as diamond.
• Polycarbonate does not blunt bullets so has to do most of its work by friction and plastic deformation in radial flow. Eventually if such elastomers stop the bullet they then spring it backwards about 5mm. Cylindrical punches have been tested and created a crack channel 1.4 the width of the impactor and permanently stretch it as far as 3.5 times the width of the impactor.
• Plastics in laminated glass absorb energy by out of plane plastic deformation through in plane membrane stretching, or interlaminar fracture by translaminar tensile failure (tearing) or out of plane interlaminar shear (delamination).
• The military have experimented with polyurethane instead of polycarbonate.
• Polymers like polycarbonate, acrylic and polyurethane tend to need to be too thick for high threat weapons.
• A specialist option for transparent armour is a transparent ceramic like spinel, sapphire or aluminium oxynitride (ALON). Sapphire or ALON disruptor attack faces can cut penetration depth by a quarter to half, but they are hard to obtain in large panes.
• Sapphire glass is available from Saint-Gobain as SAFirE for NIJ iii-IV and Stanag levels, which has 3.97t/m3 density, 435GPa Youngs modulus, 1.035GPa flexural strength, 175GPa shear modulus, 0.29 Poisson ratio, 2GPa compressive strength, 2t/mm2 Knoop hardness and 2MPa fracture toughness, it is weatherproof, hard to melt and drill, and cold at 0.4W/cmK, but you cannot buy it big panes anyway. – it comes in maximum 12″x20″ panes 0.1-0.3″ thick. It is aimed at military vehicles for lightness and biocompatibility of spall.

• Tempered glass is to be avoided in ballistic glazing as it crumbles instead of leaving large shards like annealed glass to absorb impact. Tempered glass is really just to avoid killing your kid when they fall on it. It bends four times more than annealed glass before breaking and is four times stronger, but this should never happen with security glazing anyway as you do not want it popping out the frame. So its main benefit is anti vandalism although even that is questionable as it can be exploded with a centrepunch. Although tempered glass raises the force needed to break the glass, once it cracks its tiny shards expand as compression is released, stiffening the interlayer in laminated glass temporarily before their force delaminates them.
• Polycarbonate is tougher than glass, ductile with high yield strain and strain hardening. It eventually fails through dishing, deep penetration, petalling, cone cracking and plugging, or it succeeds by plastic deformation. Thin pane failure is by dishing then penetration, while thick pane failure if by penetration then yawning penetration, both ending up with petalling; for cylinders failure is by cone cracking on thin panes and by plugging on thick panes. A test on polycarbonate with 7.62 AP bullets at 701m/s found it partly closes back up behind it to a 4mm wide cavity inside a 16mm crack, taking 0.5-0.7ms depending on speed, with 80% of penetration obtained in the first 50% of time, and half speed lost in 50% of time and speed lost linearly over time.

Standards

EN1522

• In barriers such as window frames the UK uses BS EN 1522 and 1523 rated from FB1 to FB7 and FSG (shotgun slugs). The FB ratings correspond to the BR ratings of EN1063 glazing.
• Scrutinise the testing of any ballistic frame you buy, as traditionally vendors were allow to shoot the glass with the next level down of calibre and if that didn’t blow the glass out the frame the frame was deemed the same rating as the glass.

EN1063

• The UK’s ballistic glazing standard is BS EN1063 in BR ratings:
  • handguns BR2-BR4,
  • low power rifles BR1 & NATO M16 G36 G3 rifles BR5-BR7 and
  • hunting shotguns SG.
• The test is usually 3 shots at 5 or 10 metres spaced in a 12cm triangle.
• BR1-4 are short arms and above that are long arms. BR4 and BR6 are dual ratings that require the sample to be softened up with the previous rating and then hit with the higher threat weapon. BR2 is nearly four times as strong as BR1. BR3 is 47% stronger than BR2. BR4 is nine times stronger than BR1 and 60% stronger than BR3. BR5, despite being for the highest rated velocity rifle, is only two thirds the strength of shotgun ratings. SG2 is a three shot upgrade of SG1. BR7 is effectively an armour piercing upgrade of BR6. Only BR6-7 are stronger than SG ratings and BR5 is weaker, so only a BR6 can be roughly substituted for SG to stop shotguns as well as handguns regardless of whether you want to stop rifles. All levels are incremental so for example a BR7 stops a BR5 round. An AK47 falls between BR5 and BR6.
• They have an S/NS suffix for spall/no spall as some glass comes with polycarbonate inner layer to catch splinters called ‘spall’. No-spall laminated glass is very thick and heavy as it is over-engineered compared to penetration at up to twice the thickness to stop splinters. Unfortunately as in a STHF scenario there are no hospitals, and you do not want to risk unnecessary intimidation from family seeing the inner pane exploding, the dearer no spall glazing is recommended.
• GGF say typical thicknesses of ballistic laminated glass or polycarbonate glass to achieve EN1063 spall or no spall ratings are:
  • BR1 S = 14mm,
  • BR2 S = 22mm,
  • BR3 S = 24mm,
  • BR4 S = 33mm,
  • BR4 NS = 54mm,
  • BR4 NS polycarbonate glass = 21mm,
  • BR5 S = 37mm,
  • BR5 NS = 58mm,
  • BR5 NS polycarbonate glass = 32mm,
  • BR6 S = 50mm,
  • BR6 NS = 71mm,
  • BR6 NS polycarbonate glass = 38mm,
  • BR7 S = 56mm,
  • BR7 NS = 81mm,
  • SG1 S = 33mm,
  • SG1 NS = 54mm,
  • SG1 NS polycarbonate glass = 21mm,
  • SG2 S = 50mm,
  • SG2 NS = 71mm, and
  • SG2 NS polycarbonate glass = 38mm.
• These thicknesses suggest SG1 approximates BR4 and SG2 approximates to BR6, but lead slugs devastate laminated glass so BR4 is too much of a gamble unless you are confident you will only face lead shot. BR5 would be much safer for one shot and BR6 is the minimum level to see off multiple shots.
• BR4 is not always as strong as NIJ II. BR5 can be stronger than AK47 glass but weaker than UL752 7. BR6 is not always as strong as NIJ III and is weaker than a UL752 8 but stronger than a UL752 5. BR7 is stronger than NIJ IV.
• The no spall rating increases thickness by about 42-63%.

BS5051

• You may still come across the old BS5051 from:
  • G0 (9mm) through G1 (.357 magnum) to G2 (.44 magnum),
  • R1 (5.56 rifle) to R2 (7.62 rifle), and
  • S86 for 12 gauge solid lead slug.
• Many UK customers still have out of warranty BS5051 products and they are still sold, typically alongside the new ratings. Safetell still sells BS5051 bank counters.

ST-STD-01.01

• The USA diplomatic standard SD-STD-01.01 for barriers such as windows includes ballistic rating as well as manual attack, so if you find a door or window to this standard, perhaps for its mob attack protection, you know you have some ballistic protection.

WMFL

• Walker McGough Foltz Lyeria is a USA manual attack standard which at the highest level (I) includes 25 rounds from a .44 magnum as part of a 60 minute manual attack.

UL752

• The main USA ballistic standard is Underwriters Laboratories 752. Of note, level 6 is level 1 9mm handgun ammo but from a submachine gun and five shots instead of one and at 427m/s instead of 358m/s. Level 4 stops more energy than a level 5 but the lighter and faster level 5 .308 is seen as a more dangerous bullet than the level 4 .30 calibre. Shotgun and handgun ratings must stop 3 shots, armour piercing must stop 1 shot, rifles must stop 1 shot except levels 4 and 5 with 1 shot. UL752 does not have an equivalent of BR1 or NIJ type I (for .22 rifles or no 4 lead shot).

NIJ 0108.01

• NIJ is a USA ballistic barrier standard similar to NIJ 0101.06 for ballistic vests, ranging from type 1 to type 4. The types are:
  • I for low power rifle and .38 special,
  • IIA for slow .357 magnum & 9mm,
  • II for fast .357 magnum & 9mm,
  • type IIIA is .44 magnum & 9mm submachine gun,
  • III for high power rifle and
  • type IV is armour piercing rifle.
• All levels are incremental so for example a type II stops a type I round. Shotgun lead shot is covered by types I to IIA. Five shots are required or one for armour piercing.

GOST R50963-96

• You may occasionally come across the Russian standard GOST which is aimed at vehicles.

Equivalence

• The rough equivalence of standards with energy levels is:
  • BR1 (168J) / FB1 (.22 LR rifle lead round nose 2.6g 360m/s) / NIJ I (most .25 or .32 calibre handguns and 9mm Luger or 12 gauge no 4 lead shot or 22 LRHV lead 2.6g 320m/s or x .38 special RN lead 10.2g 259m/s x 5 shots) = .22 LR rifle
  • BR2 (640J, Parabellum) / FB2 (9mm Luger full steel jacket round nosed lead core 8g 400m/s) / G0 (Uzi 9mm) / GOST 1 / UL752 1 (9mm x 19 copper FMJ lead core 8g 1,175 ft/s x 3 shots) / NIJ IIA (12 gauge 00 buckshot, .45 auto, .38 special, .40 S&W FMJ, .357 magnum JSP 10.2g 381m/s or 9mm FMJ RN 8g 332m/s x 5 shots) = 9mm
  • UL752 6 = 9mm x 19 copper full metal jacket lead core Uzi 8g 1,400 ft/s x 5 shots (729J)
  • BR3 (943J) / FB3 (.357 magnum full steel jacket coned lead core 10.2g 430m/s) / G1 / UL752 2 (.357 magnum 9mm jacketed soft point 10.2g 1,250 ft/s x 3 shots) / NIJ II (.357 magnum JSP HV 10.2g 425m/s or 9mm FMJ RN HV 8g 358m/s x 5 shots) = .357 magnum
  • BR4 (1,510J) / FB4 (FB3 + .44 Rem magnum full copper alloy jacket flat nose lead core 15.6g 440m/s) / G2 (Remington 12 gauge) / UL752 3 (.44 magnum lead semi wadcutter gas checked 15.6g 1,350 ft/s x 3 shots) / NIJ IIIA (.357 Sig FMJ FN, .44 magnum SJHP SWC gas checked 15.55g 426m/s or 9mm submachine gun SMJ/FMJ 8g 426m/s) = .44 magnum
  • BR5 (1,805J, .223 Remington) / FB5 (5.56 x 45 NATO rifle SS109 AP full copper alloy jacket pointed lead core steel penetrator 4g 950m/s) / R1 (SA80) / GOST 3 / UL752 7 (AR15 .223 / 5.56 x 45 rifle copper full metal jacket lead core military ball 3.56g 939m/s x 5 shots)
  • G3 AK47 (1,991 J, 7.62 x 39 M43 rifle 7.9g 710 m/s)
  • SG1 (2,734J, 12 gauge 31g solid lead Brenneke slug 1,312 ft/s) / S86 = 12 bore
  • SG2 (SG1 x 3) / FSG (12/70 31g solid lead slug 420m/s) / UL752 Shotgun (buckshot 00 lead 42g 1,200 ft/s 12 bore 3 strikes + 12 gauge rifled lead slug 28g 1,585 ft/s 3 strikes)
  • GOST 2 = AK74 5.45 steel core
  • GOST 3 / G3 = AK47 heat treated
  • BR6 (3,272J, .308 Winchester) / FB6 (FB5 + 7.62 x 51 NATO rifle full steel jacket pointed lead core 9.5g 830m/s M80) / R2 (SLR L1A1) / GOST 4 (AK47 AP steel core) / NIJ III (.223 Remington 5.56 FMJ, .30 Carbine FMJ, 12 gauge rifle slug, .308 FMJ Winchester, 7.62 x 51 FMJ M80 9.7g 838m/s x 5 shots = UL752 8 = level 5 x 5 shots
  • BR7 / FB7 (3,295J, 7.62 x 51 NATO rifle AP full copper alloy jacket pointed steel hard core 9.8g 820m/s) / GOST 5 (Dragunov SVD 7.62 x 54 AP) / UL752 8 (7.62 x 51 FMJ) / NIJ IV (7.62 x 51 AP, .30 AP M2 10.8g 868m/s x 1 shot) / NIJ M14 (7.62 x 63 AP30.06) = 7.62 rifle steel core / UL752 9 (30.06 rifle soft core full metal jacket APM2 2,715 ft/s 10.8g)
  • UL752 5 = 7.62 x 51 308 Winchester/M80/AR15/AK47 rifle lead core military ball copper full metal jacket 9.7g 2,750 ft/s 1 shot (3,409J)
  • UL752 4 = 30.06 rifle lead core soft point 11.7g 2,540 ft/s 1 shot (3,507J)
  • UL752 10 = .50 rifle lead core full metal copper jacket military ball 45.9g 483 m/2 x 3 shots (5,351J)

• By comparison with ballistic energy, with the lowest energy threat being the low power rifle at 168J, the highest rated stab vest is 43J, so four times weaker.

USA DoD

• The USA DoD navy security glazing handbook specification for ballistic glazing is:
  • For low threat (9mm):
    • 6mm laminated strengthened glass – 6mm air gap – 9mm polycarbonate insulated unit,
    • 28mm laminated glass,
    • 25mm laminated polycarbonate, or
    • Polycarbonate glass of:
      • 6mm chemically strengthened laminated glass – 6mm polycarbonate,
      • 6mm strengthened glass – 9mm polycarbonate, or
      • 5mm strengthened glass – 6mm annealed glass – 9mm polycarbonate
  • For medium threat (.44 Magnum):
    • Insulated unit of:
      • 12mm laminated strengthened glass – 6mm air gap – 12mm polycarbonate insulated unit, or
      • 6mm laminated strengthened glass – 6mm air gap – 19mm polycarbonate, 
    • 44mm laminated annealed glass,
    • 31mm laminated polycarbonate, or
    • Polycarbonate glass of:
      • 10mm chemically strengthened laminated glass – 12mm polycarbonate,
      • 6mm strengthened glass – 10mm annealed glass – 10mm polycarbonate,
      • 5mm strengthened glass – 6mm annealed glass – 9mm polycarbonate,
      • 22mm laminated annealed glass – 6mm polycarbonate,
      • 22mm annealed glass – 6mm polycarbonate,
      • 3mm strengthened glass – 8mm annealed glass – 12mm polycarbonate, or
      • 3mm chemically strengthened glass – 16mm laminated annealed glass – 6mm polycarbonate
  • For high threat (12 gauge shotgun / 7.62mm rifle 147 grain M80 ball):
    • Insulated unit of:
      • 19mm laminated strengthened glass – 6mm air gap – 24mm laminated polycarbonate, or
      • 6mm laminated strengthened glass – 6mm air gap – 19mm polycarbonate, 
    • 50mm laminated annealed glass, or
    • Polycarbonate glass of:
      • 3mm strengthened laminated glass – 19mm laminated annealed glass – 10mm polycarbonate,
      • 25mm laminated annealed glass – 6mm polycarbonate,
      • 28mm laminated strengthened glass – 5mm polycarbonate, or
      • 28mm laminated annealed glass – 10mm polycarbonate.
      • Notably they do not say shotguns or rifles can be stopped with only polycarbonate.
  • For very high threat (7.62mm rifle 150 grain lead core FMJ) use polycarbonate glass:
    • 41mm laminated annealed glass – 6mm polycarbonate, or
    • 3mm strengthened glass – 28mm laminated annealed glass – 5mm polycarbonate
  • This suggests the thinnest polycarbonate glass to stop a shotgun for the UK threat environment is 31mm.
• Frames (and ballistic doors shutters & blinds) must be BS EN1520. Ballistic glazing can come in double glazed units, although think about the residual resistance to manual attack after an edge shot when the bullet punches the aluminium spacer.
• Check how resistant the frame is, as without 6mm steel construction or steel inserts it may be a way around the glazing. Beads should be 5mm steel. Steel costs over twice as much as aluminium but aluminium cannot take much of a beating without the help of steel.

Shotguns

• Shotgun lead shot can come out six times the weight of a .38 but at the same speed, and a 12 gauge Brenneke lead slug is three times the weight of a .357 but comes out at the same speed.
• BR4 should stop a 44 magnum and might even stop a shotguns unless they use something like multiple 12G slugs that need an SG2 rating which probably also stops a 5.56 rifle – there are no guarantees as different bullets need different layer designs. The safest bet against shotguns is BR6 as it is the only standard that also stops handguns which is not weaker than SG standard. Bear in mind that the USA UL752 standard for shotgun resistance assumes heavier slugs up to 42g buckshot and the US Navy standard treats 12 gauge shotguns as for rifles as a high threat rating. The USA NIJ0108 standard explains that level I (similar to EN1063 BR1) rated for LR rifles should also stop 12 gauge no 4 lead shot from a shotgun, level IIA rated for .38 magnums (or UL752 level 2 or EN1063 BR3-BR4) should stop 00 buckshot and level III rated for high power rifles should stop a shotgun slug.
• Especially as SGTF could see multiple point blank shots threatening family and you don’t know what is coming out the barrel then if you can afford it and find big enough frames you should err on the side of overspecifying so probably ideally specify BR6 NS, although there is much more choice in the consumer market at BR4. However, for shotgun threats as there are not so many slugs about in the UK you could justifiably choose to just protect against the more available lead shot, equivalent to a .38 which would need BR4, covering you for lead shot, low power rifles and handguns in the hope that nobody turns up with shotgun slugs, NATO rifles or machine guns.
• The old BS5051 S86 rating is not much use for preppers as it only assumes one shot from a shotgun at 10 metres. There is also standard ISO16935 for ballistic glazing which has the choice of three ratings SG1 to SG3 for shotguns for 1-3 strikes, and an RS rating for reduced spall not penetrating a witness foil.
• You can stop some higher power rifles with laminated glass 50mm thick weighing 117kg/m2 but it is not rated against shotguns and would spall glass splinters into your face.

.50 calibre

• Nobody outside the military protects against .50 rifles as although the speed is the same as other rifles the weight is about five times more so the energy is five times higher and nobody wants that sort of cost and thickness.

Products

• The ballistic glazing market is dominated by Saint-Gobain, Asahi, Armassglass, Binswanger and Guardian, with other players including AGP, Armortex, Centigon, Consolidated, Fuyao, Guangdon Golden, Nippon Sheet, Schott, STEC, Taiwan Glass, Total Security.
• Similar products as for manual attack are used for ballistic glazing. In the USA occasionally you will come across acrylic being used for level UL752 levels 1-2, but often as the core faced with polycarbonate. Acrylic is best left for hamper screens where it is used in 10mm to deter vaulting and physical violence. Polycarbonate is more popular for levels 1-3. Laminated glass or poly glass is used for levels 1-8. Glass is preferred as the attack face to soften up bullets and polycarbonate for the protected face as a spall catcher and as it stretches to catch the bullet it tends to hold the glass in place without delaminating.
• Raytheon’s ALON, now sold by Surmet for some £10 per square inch in up to eight square feet panes, is transparent aluminium based ceramic which can stop a .50 AP round in 1.6″, is three times harder than glass, 40% more transparent for night vision gear and 50% lighter, so a great but expensive (four times dearer than laminated glass) attack face for high energy rounds; a slightly weaker alternative is Spinel and a slightly weaker alternative to that is sapphire; they are put on the front of glass which has a poly spall layer on the protected face; they rely on disintegration with a bigger explosion of glass back towards the shooter to absorb energy so you cannot see through a shot pane.
• Cardea’s Hammerglass has two ballistic thicknesses including 23mm and 39mm.
• ESG Secure can fit LPS1270 123 (SR3 equivalent) and EN1063 BR2 into 20mm poly glass in case you only expect 9mm handguns or low power rifles. If you can stretch to 21-31mm there are products which can give you BR4 against .44 magnums and one or more shots from a shotgun. Below about 30mm, though, ballistic poly glass is vulnerable to multiple shots which will eventually either penetrate or facilitate breaking in, however all ESG’s ballistic products also have dual EN356 & LPS1270 forced entry ratings. They do not advertise separate ballistic products hence there do not seem to be shotgun or high power rifle ratings beyond what is achieved from forced entry glass.
  • P8B/P7B + LPS1270 001 + EN1063 BR1 13mm (they give both EN356 ratings)
  • P8B + LPS1270 112 + EN1063 BR2 18mm
  • P8B + LPS1270 123 + EN1063 BR2 20mm
  • P8B + LPS1270 224 + EN1063 BR4 39mm
  • P8B + LPS1270 235 + EN1063 BR5 57mm
• Global Security Glazing make:
  • laminated ballistic glass to
    • UL1 32mm
    • UL2 49mm
    • UL3 54mm
    • UL4 55mm
  • Secur-Tem ballistic poly glass to
    • UL1/NIJ IIA 19mm
    • UL2 24mm
    • UL3 28mm
    • UL4/NIJ IIIA 31mm
    • UL5 33mm
    • NIJ III 40mm
    • NIJ IV 52mm
    • UL8 61mm
  • Lexgard lam poly to:
    • UL1 19mm
    • UL2 23mm
    • UL3 32mm
• Pilkington Optilam can come in spalling ballistic versions 11.5-73mm thick, including:
  • BR2 S 20mm
  • BR3 S 24mm
  • BR4 S 26mm
  • BR5 S 37mm
  • BR6 S 46mm
  • BR7 S 73mm
• Saint Gobain make:
  • Vetrogard Bullet laminated glass to:
    • BR1 S 13mm
    • BR2 S 22mm
    • BR3 S 23mm
    • BR4 S 32mm
    • BR5 S 36mm
    • BR6 S 50mm
    • BR7 S 85mm
    • SG1 S 32mm
    • SG2 S 50mm
    • BR2 NS 31mm
    • BR3 NS 44mm
    • BR4 NS 54mm
    • BR5 NS 58mm
    • BR6 NS 73mm
    • BR7 NS 81mm
  • Polygard Bullet poly glass to:
    • BR1 NS 18mm
    • BR4 NS + SG1 NS 21mm
    • BR5 NS 32mm
    • BR6 NS + SG2 NS 38mm
  • Polygard can take you to EN1063 BR4 in 21mm poly glass which would buy you time to react to all but the strongest rifles and most sustained shotgun attackers while they reload.
  • Vetrogard Pro laminated glass combines ballistic & manual attack
    • BR4 S + SG1 S + P8B 35mm
    • BR3 NS + P8B 44mm
    • BR6 S + SG2 S + P8B 51mm
    • BR4 NS + P8B 54mm
  • Polygard Pro poly glass combines ballistic & manual attack
    • BR4 NS + SG1 NS + P8B 21mm
    • BR6 NS + SG2 NS + P8B 38mm
  • The same group, Hamilton Erskine, also make Tecdur Ballistic Glass in BR1 to BR6, SG1 to SG2 and AK47 and can include EN356 or LPS1270 ratings from P1A to SR6, theoretically available as laminated glass but probably all poly glass.
• Safetell have for some time sold ballistic fixed panels to FB6 & BR6, but now also sell secondary glazing up to FB6/BR6 using glazing 13.5-42mm thick, and, even better, they are horizontal sliders.
• Selectaglaze ballistic windows are fixed demountable secondary glazing to EN1522/3 BR4 with 22mm polycarbonate glass.
• If you do not mind the industrial look you might be able to source ballistic roller shutters for windows from abroad, such as the Collbaix Diamond BL to RC5 & EN1522 FB4 or Extreme version to RC6 & FB6.
• Silatec suggest ballistic glass costs up to ten times more than normal thermal glass, with price ranges upwards of 300EUR/m2 for handguns, 600EUR/m2 for rifles and 900EUR/m2 for AP rifles, adding 20% for solar gain and 20% for low-E coatings. They recommend ordering sizes between 1 and 6 square metres to avoid excess setup or handling. They point out that by paying more for poly glass the reduced weight saves you on installation costs. To stop armour piercing bullets typically needs an increase of about 75% thickness and 85% weight as you need a higher proportion of glass and more of everything.
• Laminated glass is increasingly efficient at stopping multiple shots from handguns and low power rifles as it thickens, but its thickness-energy ratio tails off once it takes the dense energy of high power rifles or is softened up by multiple shotgun hits; the problem is mostly weight of round. Unfortunately, to stop multiple shotguns slugs you need to stop a high power rifle and that needs some 50mm of laminated glass weighing 117kg/m2; the efficiency of BR5 laminated glass against handguns and low power rifles is useless when it cannot stop a sustained attack by shotgun – to do that you need SG2, which is effectively BR6 against high power rifles. Its thickness has to increase by about half to two thirds to become non spall so is particularly unsuitable for situations where you may be within a few feet of the glass unless you are happy with the weight and thickness and its effect on cost and choice of frames. The problem seems to be that it is ‘all blunt and no catch’ – it is forced to use excessive thicknesses of broken glass to not only blunt the bullet to reduce energy density but also to decelerate it like a net with only thin PVB interlayers to do so.
• Poly glass is a better compromise as it keep enough glass to blunt the bullet but uses polymer as proper layers instead of as merely interlayers, literally eating the bullet. It is especially efficient against shotgun slugs and better against non AP rifles, yet offers no real improvement compared to lam glass against low power rifles. Poly glass rated EN 1063 SG2 to stop shotguns is typically 38mm thick weighing 83kg/m2 and would be equivalent to BR6 to stop some rifles.
• See this table of ratings, energies (joules) and thicknesses with corresponding energy of rounds stopped per mm for spall allowed layups (some energy penetrates via spall):
  • BR1 – 168 x 3 – 13mm lam glass = 13J/mm /
  • BR2 – 640 x 3 – 22mm lam glass = 29J/mm
  • BR3 – 943 x 3 – 23mm lam glass = 41J/mm
  • BR4 – 1,510 x 3 – 32mm lam glass = 47J/mm / 24mm poly glass = 63J/mm
  • BR5 – 1,805 x 3 – 36mm lam glass = 50J/mm / 35mm poly glass = 52J/mm
  • SG1 – 2,773 x 1 – 32mm lam glass = 87J/mm / 24mm poly glass = 116J/mm
  • BR6 – 3,272 x 3- 50mm lam glass = 65J/mm / 38mm poly glass = 86J/mm
  • SG2 – 2,773 x 3 – 50mm lam glass = 55J/mm / 38mm poly glass = 73J/mm
  • BR7 – 3,295 x 3 – 85mm lam glass = 39J/mm / 74mm poly glass = 45J/mm
  • UL4 – 3,507 x 3 – 50mm lam glass = 70J/mm
• Polymer glasses like laminated polycarbonate, polycarbonate glass or ionomer glass allow thinner thicknesses. Polycarbonate glass is better at soaking up the 30.06 rifle at UL 4, whereas ionomer glass is better at swallowing .44 magnums and high velocity 9mm at NIJ IIIA, and laminated polycarbonate has a slight edge with 9mm Uzis at UL 6, but ultimately it comes down to cost, lifespan until delamination and weathering, with lam poly resisting cracking, poly glass better at weathering and ionomer glass good at weathering too plus longer lasting:
  • NIJ I – 11.6mm ionomer / 21mm poly glass
  • NIJ IIA – 18mm ionomer / 19mm poly glass
  • NIJ II – 18mm ionomer
  • NIJ IIIA – 21.4mm ionomer / 31mm poly glass
  • NIJ III 37.9mm ionomer / 39mm poly glass
  • UL 1 – 21.6mm ionomer / 19mm poly glass / 19mm lam poly
  • UL 2 – 22.4mm ionomer / 24mm poly glass / 22mm lam poly
  • UL 3 – 25.4mm ionomer / 28mm poly glass / 32mm lam poly
  • UL 5 – 36.2mm ionomer / 33mm poly glass
  • UL 4 – 36.4mm ionomer / 31mm poly glass
  • UL 6 – 36.5mm ionomer / 32mm lam poly
  • UL 8 – 45mm poly glass
  • UL 7 – 49mm poly glass
  • NIJ IV – 52mm poly glass

Manual attack:                     

Tips

• To resist manual attack windows may need bars, security blinds, grilles (RSG’s 14000 collapsible grille is rated SR3 to match a brick wall’s maximum strength). Ultimately normal domestic windows probably cannot be secured without bars or grilles. Remember bars need to be tightly spaced enough to stop the typical skinny youth who burgles. Also consider that bars are glorified rebar so like reinforced concrete without the concrete – would you accept a wall like that?

• Although polycarbonate is vulnerable to chemical attack, this is not anticipated in a SHTF scenario where intruders are hungry as opposed to skilled, so it could be acceptable to not clad in glass.
• Ideally use small panes of laminated glass bonded to the frame.
• Windows must lock, otherwise burglars will find a way of manipulating the handle through a gap.
• Hinges must be backed up by dog bolts or hinge claws.
• External beads should ideally be avoided otherwise they need screwing, clipping or taping.
• Security glazing needs at least a one inch bite into the frame.
• Consider how the fixings, glazing, hinges, locks and frame are made and how they weaken the barrier.
• Keep an eye out for exposed hardware, gaps, weathering and vulnerable beading.
• The joint between frame and wall should be shielded.
• Ask yourself how much abuse timber or upvc will really take compared to metal.
• If you have to prioritise replacing glass, start with panes near door locks and windows without locking handles.
• Realistically, given the cost of a panic room as an alternative, you probably would not want to go further than anti bandit glazing strong enough to stop spalling from a blast, shotgun pellets and opportunistic burglars, then have shuttering ready for when you expect trouble.
• Just out of interest, a typical high street jeweller anti bandit glazing is 11.5mm laminated glass, rated to LPS2081 SRA or SRB domestic risk and PAS24 and SBD as a housebuilder glass, and not even achieving LPS1175 SR1, as pocket tools can tear out a man size hole in under a minute. Under sledgehammer attack four blows punched it out the frame.
• We see in one video a hand hole made in 7s by a lump hammer from tool group C through 13mm anti bandit glass (probably rated P6B), compared to 17mm LPS1270 poly glass (probably rated P8B or SR2).
• LPS1175 manufacturers typically specify something like Tecdur DC46 (46mm poly glass) for doors with panic bars (although glazing is advised against altogether), as otherwise bodily entry is gained by opening the inside handle through a tool or hand hole – even though a body hole could not be made even with much thinner glazing.
• A common poly glass for forced entry is three ply, with poly core and balanced glass each face.
• Ionomer glass is mainly for manual attack as it helps chew up saws. It is mainly used in symmetrical laminates. It works best as a thick core.
• Manual attack frames should be anchor bolted to the wall. Ideally should be the stops or beading, although they must be removable ones such as a taper bolt. Sleeved space expansion anchor bolts are too weak for manual attack.
• Interlayers are either polyester like PVB, or ethylene vinyl acetate (EVA), or resin (polyester or polyurethane), or ionomer (eg Sentryglas) or polycarbonate.
  • In three ply laminated glass Sentryglas is used in 2.28mm thickness for UL972 & EN356 P1A-P5A and 4.56mm for low classes in ASTM F1233 & HPW TP-0500.03 & P6B-P8B, and 6.84mm for higher classes in ASTM F1233 & HPW TP-0500.03 and risks beyond EN356. The 1.52mm Sentryglass is for ballistic multi-plys. Beware that Sentryglas can be weaker than PVB for manual attack, for example, 6.8mm lam glass with PVB interlayer gets EN356 P2A but with Sentryglass it fails even P1A. With Sentryglas Xtra 6.8mm (with 0.76mm interlayer) it only gets P1A and bizarrely the thicker 6.9mm (with 0.89mm interlayer) fails P1A. It seems to be so stiff it ‘hits’ the missile instead of flexing to catch it. For FEBR risks where glass will be softened up by bullets first the strongest ionomer against ASTM F1233’s 9mm 3 shots is about 6.84mm and against 5-aa1’s 7.62mm 5 shots is about 6.84mm although 4.56mm is as good as a 6.84mm PVB. Ionomer is so stiff that it is the best bet for hot climate or where torch attack is expected as it buys time by simply softening to PVB standard, but it is bad news in cold weather or where freezer sprat attacks are expected as it becomes too brittle.
  • EVA quickly yellows and hazes and is half the strength of PVB so tends not to be used.
  • The strongest manual attack PVB at room temperature is about 4.56mm whether a ballistic attack is included or not.
  • For anti bandit high impact short delay threats 1.52mm interlayer is used whether PVB or ionomer, and 7.5mm laminated glass can, for example, pass UL752 to handle a 5lb steel ball falling 40′.
  • PVB can be made stiffer by reducing plasticiser, which is sometimes used with tempered glass to avoid collapse.
  • PVB does not stick to Sentryglas or polycarbonate so for those layers thermoplastic polyurethane (TPU) is used.
  • PVB comes in multiples of 0.38mm foil and is made of about 78% vinyl butyral, 20% vinyl alcohol and 2% vinyl acetate. Plasticisers are added to increase elasticity, or reduce to increase strength and stiffness. It starts weakening at room temperature.
  • Ionoplast foil comes in 0.89mm / 1.52mm / 2.29mm / 3.05mm thicknesses.
  • For impacts under 25m/s the strength of laminated glass is determined by the thickness of layers behind the first interlayer, and for faster non ballistic impacts by the thickness of the interlayer.
  • High impacts either bounce off Sentryglas or obliterate it, whereas on PVB they penetrate but leave the pane in place, suggesting ‘glassy’ Sentryglas needs to be backed up by ‘rubbery’ PVB.
  • Sentryglas lasts longer before haze, delamination or yellowing occurs but is more expensive.
  • Sentryglas has five times more tear strength than PVB and 100 times the stiffness.
  • Sentryglas Poisson ratio is 0.448 at room temperature so does shrink quite a bit sideways when stretched longways.
  • Sentryglas Youngs modulus is 628MPa at room temperature for 1s, which is over three times less stiff than polycarbonate, two thirds the stiffness of polyurethane.
  • Sentryglas needs to be about 20% of the layup where used instead of poly in manual attack laminated glass judging by a DoS memo on SD-ST.01.01.
  • Laminated glass breaking strength is the same as the monolithic equivalent of adding up the glass layers, so you are not making glass very hard to break, just holding the pieces together.
  • The less energy stored in glass the bigger the shards when it breaks and thus the stronger it stands up on the interlayer.
  • PVB is a thermoplastic so softens when hot. Polyurethane is an elastomer so can stretch when hot then snap back when cool. Resign is a thermoset so deforms and stays that way when hot.
  • Resin is expensive and does not like being hit when cold.
  • EVA is the least yellow and the most ductile so can stretch to take energy away from fixings but eventually would thus come out the frame or tear; it is also survives best against solar radiation to prevent excess deflection. PVB and Sentryglas have greater tensile strength and stiffness although Sentryglas is the stiffest. Sentryglas copes best with heat and humidity and PVB the worst, deflecting more. PVB is by far the most yellow, deflects the most after UV exposure, and is twice as strong as EVA and SGP is about 75% stronger than PVB. PVB could stretch about three times its length before snapping, SGP about four times and EVA about nine times. SGP is stiff enough that it rarely gets to that stage. SGP’s Youngs modulus (stiffness) is around 165 times higher than PVB, although that does not in itself mean it can absorb more energy, it is just transmitting it more to beading.
  • TPU is strong and tough but expensive so reserved for ballistic glass. It is ideal for glueing glass to polycarbonate. Temperature rather than humidity increases deflection for all these interlayers.
  • Typically when laminated glass breaks the protected face breaks first under tension followed by the attack face under less force, which retains some strength under compression held up by the interlayer.
  • PVB with low plasticiser has low stiffness and low ductility so offers the worst of both worlds.
  • SGP has been tested 101 times stiffer than PVB against an hour of wind, but in real world attacks lasting only fractions of a second PVB does not have time to stretch; for example, a 5s wind test shows SGP is only 13 times stiffer than PVB.
  • Interlayers can theoretically delaminated by edge steam attack or D201 non-ionic surfactant.
  • Interlayers tend to stay stiff under attack as point loads do not have time or area to stretch the whole foil.
  • As PVB allows glass to deform more by shearing slightly across both sides of the foil it also has to be more ductile to allow that stretch. SGP only allows glass to deform about 44% as much so can be less ductile. Glass bends about 13% more before breaking with SGP interlayer than PVB and needs about 25% more force to do so.
  • EVA lets laminated glass bend about 55% more than PVB.
  • PVB lets laminated glass bend typically 67% more than SGP before breaking, so taking more energy away from the interlayer and beading but risking popping out.
  • SGP typically increases laminated glass ultimate load about 15% compared to PVB but mainly it stops glass bending so much by the time it reaches that point of failure.
  • Architectural PVB like Solutia’s Saflex DG41 is the same strength as ionoplast like Sentryglas. It cannot cost effectively be made stiffer as to reduce its plasticiser any more would literally stop it flowing off the production line
  • Eastman Saflex RB41 is a typical normal strength PVB foil.
  • PVB stretches the most when unconstrained by being glued to unbroken glass, but still springs back; this is what you see in attack test videos, but by then some glass has come off and the interlayer has torn so it can be pushed into a bigger hole. They way to stop this would appear to be stiffness and strength so that it does not tear, and even if it does it cannot be successfully shoved.
  • Interlayers normally stick to glass due to chemical bonds between glass’s silanol groups and polymer’s alcohol groups.
  • There is a concern that Sentryglas does not adhere to glass as strongly as PVB does, so is perhaps best used in big thickness for its own strength like a polycarbonate layer and/or stuck to polycarbonate.
  • Under low strain DG41 PVB starts off stiffer than SGP but eventually SGP survives twice as much strain before snapping.
  • Urethane interlayer is good for rifle resistance in the cold. Polyether urethane is the only interlayer used to glue polycarbonate.
  • When laminated glass is hit, depending on total and concentrated energy for how stages it progress through, first it bends, then shatters, then the interlayer stretches and glass delaminates or even spalls in a jet, and finally the interlayer tears. The fact that glass bends and the interlayer stretches is good for absorbing energy, but eventually the stretchiness becomes a snap, and the shattering leaves the interlayer holding together weakly or unbound shards and they are sharp so often cut the interlayer. Shattering is easy to do but undesirable for security (except for slowing down bullets), so under any real attack leaves the interlayer doing virtually all the work and coming under attack from its own glass. Glass is bad for interlayers, and interlayers are only needed because glass is bad for security. So laminated glass is best used to protect plastic from weather and temperature while it takes the brunt of attack.
  • When a missile hits laminated glass, in one experiment with car windscreens, it was found that half the 150J energy of a 4kg steel ball dummy head at 8.7m/s, in the form of a round headed bar, is dumped in the first 2ms and 40mm deflection and if it is stopped it happens 13ms later after another 40mm travel, with about 80% of total energy soaked up by the interlayer stretching. Glass bending and shattering (c. 1.5% of energy) and spalling (c. 1.5%) does not absorb much energy, and it is too brittle to not break under attack anyway, so using tougher or thicker or thinner glass will not see off a decent attack, and in fact strengthened glass shatters smaller and so delaminates more. It is all about the adhesion and strength of the interlayer which must allow some delamination and deformation to avoid tearing. But therein lies another problem: if too sticky it will tear as it stops energy going into delamination. Funnily enough, there is a sticky strong interlayer which can also be a full blow layer that avoids the problems of glass: polycarbonate, but which has its own problems of burning and weathering.
  • Glass crack count increases as impact increases and as interlayer thins. Crack speed and number increases as impact speed increases. Attack face cracks copy and come after protected face layer cracks. What bending energy is not used in radial cracks will be used in circular cracks.
  • For single impacts anyway (easier to catch with stretchy interlayer, but which allows easier followup attack) polymer interlayers peak in strength just before their glass transition temperature:
    • ionomer prefers temperatures in the 30s-40s degrees C,
    • architectural PVB prefers about 40 degrees and loses over 70% of strength by zero degrees,
    • standard PVB prefers about 10 degrees and loses about 20% strength by 30 degrees on a hot British day (so is most suited to UK average temperature of 10 degrees), and
    • EVA prefers it as sub-zero as possible and loses 50% of its strength at room temperature.

Standards

• Low UK domestic manual attack standards for security barriers such as windows include STS 201, STS204, PAS24 and LPS2081, but are no use if a burglar is prepared to make a noise or bring tools.
• Building regs Part Q
  • Part Q requires windows within 2m of level surfaces (including roofs under 30 degree pitch lower than 3.5m) to be robust enough and use sufficient appropriate hardware to reasonably deter and resist being levered open or panes being levered out by casual or opportunist burglars without special tools.
• PAS24
  • PAS24 is the bare minimum housebuilder standard to qualify for building regs part Q.
  • It is passed by passing PAS24 or a delegated standard of EN1627 RC2, plus upgrades for UK threats, namely BS6262 and any non key locking window to have P1A glazing.
  • It is usually slightly weaker than SR1 for windows and seen as equivalent to EN1627 RC2, which is the EU standard inspired by PAS24. LPCB say for glazed products PAS24 is equivalent to RC2 and SRA or sometimes SRB.
  • So-called security windows without LPS1175 or STS 202 or equivalent certification may well be strong, but at the end of the day are not rated to even stop a screwdriver for a minute. PAS24 assumes the burglar won’t break glass or pick the lock or rip the frame out, and only tests quietly wiggling hand tools for a minute. Europe has their copycat standard called EN1627 but this does not include locks. PAS24 can be achieved with RC3 plus extra requirements, in other words RC3 is not even enough for a new build let alone a prepper. That is a reminder why EN1627 windows need RC4 (if upgraded to EN1627 not EN356 glazing) to begin to call themselves a security window and RC5 to be called a high security window. But nor is PAS24 anywhere near as strong as a brick wall either so it leaves you with a weak spot.
• SBD
  • The police security standard Secure By Design Homes 2019 requires easily accessible windows to pass PAS24 / STS204 / LPS1175 SR1 or A1 / STS202 BR1 / LPS2081 SRA, eg be key lockable and resist being screwdrivered, plus have P1A (which needs 6.5mm (sic)) laminated glass in vulnerable windows such as door glazing and windows within 40cm of doors or easily accessible non key locking escape windows. As most 6.4mm laminated glass (which used to be the standard instead of P1A) does not quite meet P1A you sometimes end up having to buy 6.8mm P2A glass. SBD requires windows to have espagnolette locks with bolts within 10cm of corners plus a third lock such as a locking handle, and should have the equivalent of hinge bolts. SBD only requires windows and garage doors to be LPS1175 A1 (eg 16.5mm laminated glass) or STS 202 SRA rated, with glazing to meet BS EN 356. Oddly, the higher SBD Gold standard only requires thinner P1A (ie 6.8mm) laminated glass on windows within 2 metres of the ground or accessible balcony, or of a roof if the window is within 3.5 metres from the ground.
  • SBD window hardware like multipoints with shoot bolts and mushrooms, and hinges, hinge protectors and friction stays, are available from Titon, Nico, Yale, Mila (a Yale distributor), Mighton, ERA, Cotswold, Securistyle Roto, Maco, GT, Kenricks and Caldwell. Mighton also do sash Securibead.
• STS 204
  • STS 204 is the Warrington lab’s route to and version of PAS24.
• LPS2081
  • LPS is LPCB’s stealth attack barrier standard. It roughly equates to SR1 downgraded to avoid excessive noise by banning hitting tools with tools. Its lower SRA rating qualifies as SBD for windows. Its SRB rating is a favourite for communal entrances to resist vandals kicking panes out.
  • LPCB say SRB is sometimes as strong as SR1 otherwise sits just below it, while SRA is always below SR1.
  • Products must stop an ellipsis test block 400 x 225 x 300mm.
  • Tool categories are A and B. Category A includes tools dangerous to windows such as a knife, punches, screwdriver 0.7kg 30cm crowbar and glass cutter. Category B adds tools such as a 0.7kg hammer, hacksaw and hand drill. The only tool which can hit another is the rubber mallet. Noisy tools are excluded. Other than that, they are the tools from LPS 1175 groups A and B.
  • Rating SRA must resist category A for one minute and SRB must resist category B for three minutes.
  • LPCB LPS standards come with a health warning which is they are a monopoly scheme operated by testing house BRE Global Ltd which you cannot inspect and reputedly include rest times. In contrast the theoretically weaker standards PAS and lower EN1627 ratings are set by BSI. You probably want to avoid LPS2081 for the same reason you avoid EN1627 RC1-3: hungry zombies are going to break glass and make a noise.
• STS222
  • STS222 is Warrington lab’s equivalent of LPS2081 for stealth attacks on barriers such as windows with ratings BR1(S) and BR2(S).
• The high UK manual attack standard for security barriers such as windows (including glazing) is LPS1175.
  • The corresponding standalone standard for glazing is LPS1270.
  • LPS1175 standard is for security barriers, but does not address thermal shock, chemical, blast, ballistic attack or static load. To resist static load LCPB recommend multipoint locking.
  • LPS1175 Ratings SR1-2 are for domestic and low commercial risk, SR3-4 for commercial risk, SR5-6 for high risk and SR7-8 for extremely high risk. For comparison, SR1-2 (or PAS or RC2-4) is normally recommended for secure hospitals, SR1 inside and SR2 outside, with SR3 reserved for the most dangerous inmates in high security hospitals equivalent to cat B prisons, and the highest rating ever needed in that setting being C20 to cover noisy tools wielded for over 20 minutes, although ratings up to RC5 or SR5 may be specified for static load resistance and robustness to take years of abuse.
  • SR1-2/3 is for amateur burglars, SR3/4 upwards for professionals, and SR5/6-8 for high value internal storage areas, so the assumption is that not many buildings will have facades exceeding SR4/5, in fact as SR4 requires reinforcement few facades could even exceed SR3.
  • LPS1175 assumes one attacker uses tools in group A-E and two attackers use tools in group F-H. Maximum tool weights per operative are 2.5kb SR1, 5kg SR2, 10kg SR3, 20kg SR4 & 25kg SR5-8. Maximum working times are 1/3/5/10/15/20 minutes.
  • Tool groups A-E are normally for external facades (group B including a 3.6V drill, group C including a 12V drill, group D including 12V power tools, group E including 18V power tools), while groups F-H are normally for strongrooms (group F including 36V power tools, group G including 54V power tools), and H tools (like diamond cores, thermic lances, 5kW grinders, concrete chainsaws) being a precursor to professionals driving, shooting or blasting their way in.
  • It would be unusual to spend enough to make the whole building resistant for many minutes to the biggest sledgehammers, pickaxes, crowbars, drills and saws, as by the time those tools work the response force should intervene, but in case they do not, perhaps because the a layer of detection failed, an inside room would be hardened against whatever are the expected threats such as hydraulics, enforcers, cutting torches, the most powerful battery tools and petrol tools. Consider that even group G 54V power tools are available from your local Toolstation: £470 for a reciprocating saw, £460 for a 5” grinder, £750 for a hammer drill, £870 for a cutoff saw, and group H tools are in the shops for a few hundred or thousands.
  • Fixings to substrates should be by M6 for SR1, M8 for SR2, M10 for SR3, M12 for SR4-5, M16 for SR6-7 and M20 for SR8.
  • Glazing, infills and external fixings can all be attacked in LPS1175 testing.
  • Testers often defeat products by breaking weak glazing, fishing through holes or cutting multipoint rods.
  • SR rated products are still sold, but the latest version of LPS1175 changed to separate tool group and time scores, so, for example, lasting 1 minute against tool group A gives an A1 rating equivalent to SR1, B3 is the old SR2, C5 is the old SR3, D10 is the old SR4, E10 is the old SR5, F10 is the old SR6, G10 is the old SR7 and H20 is the old SR8.
  • The test is passed if someone (a 16”x9” ellipsis block) could not squeeze through a hole made in the product, or if the product is smaller than the usual 16×9 hole (eg a small vision panel) then a hole cannot be made 5” in diameter or big enough to pass what is protected if smaller than that.

• STS202 is Warrington lab’s equivalent of LPS1175, and goes up to BR6 equivalent to SR6. This standard is worth knowing about as most high security residential products use STS202 rather than LPS1175 which is favoured by the commercial market. Whilst similar to LPS1175 in terms of toolsets, it has shorter attack times at the top end with BR1 lasting 1 minute, BR2 3 minutes, BR3 5 minutes and BR4 upwards lasting 10 minutes.
• There is still the old British Standard for plastic safety windows, ie polycarbonate, for anti bandit purposes to stop smash and grab through a hand hole with only very short delay times, BS 5544, which only uses a steel ball drop test. This was replaced by EN356 for windows that includes glass. It typically meant using 11.5mm or 11.3mm laminated glass rated BS6206 in a frame tested to BS5544. It tests by dropping a 2.260kg 82mm diameter steel ball 5 times from 3 m and once from 9 m in the middle of the 60cm x 60cm test piece within a 125mm circle.
• UL972 is the USA rough equivalent anti bandit standard to BS5544, tested with a steel ball drop and equivalent to UFC very low threat.
• The European manual attack standard for security barriers such as windows is EN1627.
  • The test is actually a suite of tests EN1627-30, with static and dynamic load tests first to EN1628 & EN1629, then manual attack to EN1630. Testers assume there is no point throwing themselves at a product unless it looks like it could be finished off by a barge kick or shove after a battering by tools. Many products survive load tests only to spring open under manual attack.
  • Tests include attacking hinges by punching, drilling and cutting hinge pins, prying screws out, snapping linkeages, cutting out; attacking leafs by prying edges, levering apart profiles, delaminating, smashing, cutting, prying; attacking locks by hitting or prying end of bolt, gouging leaf to access lock, cutting bolt, cutting out keep.
  • Windows can get PAS24 through EN1627 RC2 rating plus extra requirements to protect handles through glazing.
  • The corresponding European standard for security glazing is EN356 for glass, which drops a 4kg steel ball between 1.5 and 9 metres for ratings P1A TO P5A (which are really just for accidental falls). The USA burglary standard UL972 is similar, dropping a 5lb steel ball. Ratings P6B to P8B involve chopping with an axe to make a 40cm x 40cm square hole. P6B requires it to survive 30 strikes, P7B 51 strikes and P8B 71 strikes. CPNI ignore EN356 as hopelessly too weak so it is unacceptable for counter terror: even the highest rating P8B is not high security glass.
  • The tool groups for windows and attacks allowed are:
    • RC1 tests multiple slip joint pliers, screwdriver, allen keys, spanners, engineers pliers, tweezers, knives, torch, hooks, wire & string (for handles & panic bars), tape, rubber hammer & universal lock keys, all with manipulation rather than force, without hitting, gouging or levering the leaf;
    • RC2 tests pipe wrenches for twisting, bigger screwdriver, plastic wedges & wood wedges, compass saw pad saw and hacksaw for accessible hinges, allowing levering with wedges hit by rubber hammer and with bigger screwdrivers, pliers can now be used for twisting, screwdriver can now be used as chisel and crowbar, allen keys can now be used as hooks, spanners can now be used as makeshift pliers, knives can now be used for cutting, tape can now be used for drilling glass, rubber hammer can now hit all tools;
    • RC3 tests 71cm crowbar, hand drill and bigger screwdriver, allowing hand drilling (eg locks, fixings or chain drilling) and punching with pin punches and locksmith hammer (to remove hinge pins or beading) and use of two screwdrivers as levers, but crowbar can only be used as punch or lever not hammer;
    • RC4 tests lump hammer, cold chisel & wood chisel (for levering & chopping), plate shears (for thin material like scissor hinges), axe, boltcutter (eg for hinges), 14V drill (eg for pilot holes for other tools), allowing axe, wedges and chisels to be hammered hard and faster drilling and chopping and hitting frame with lump hammer or axe;
    • RC5 tests power tools: carbide tipped drill bits & core drills up to 50mm in 650W drill, 1100W bimetal blades & sabre saw, 650W jigsaw and 1100W 125mm non-diamond angle grinder are used against frame, glazing and hardware. Oddly at this level only wooden and plastic wedges are allowed despite power tools being allowed. Crucially, at RC5 upwards glazing can be attacked to see if the required EN356 rated glass survives EN1627 attack, but at this level power tools render most glazing quickly vulnerable let alone thin EN356 glass) and there are virtually no residential products anyway, although there is the slightly industrial looking Salzer S2es to RC5 or Rap Bomet Stalprofil up to RC5. Manufacturers have to upgrade to something like Grid Glass or simply use two windows, one behind the other.
    • RC6 tests heavier power tools, 1050W drill, 2300W 230mm non-diamond angle grinder, and a spalling hammer to destroy glass with up to 20 direct strikes allowed and unlimited impacts on tools, with wedges upgraded to steel. The author could find no windows to RC6, although some manufacturers claim they could make one, especially if a fixed light.
  • If you cannot find an LPS 1175 window or don’t like their industrial look then you could consider EN1627. This will probably look more domestic but you have to be careful what EN1627 actually tests. It might be the realistic option if you are not sure about the window reveal in terms of how the brickwork would take the impact through the jamb or fixing bolts or how long it would take to smash out the bricks.
  • Also consider that the UK voted against EN1627 as we would be forced to adopt it as a British Standard as a member of CEN. Police issued an interpretative document to warn about it. It does not cover some common attacks, or attacking glass for RC1-RC4. Whilst up to RC3 stealth attack is assumed, RC4 is supposed to handle noisy attacks on frames, but if you buy RC4 be careful what separate rating any glazing has. Unless you specify panic door glazing you only get the useless EN356 rating specified by EN1627. Suppliers like Silatec make panic door versions of EN1627 poly glass, for example their RC4 Panic is 40mm thick compared to the 16mm P6B normally required by EN1627 RC4. EN1627 assumes an intruder is larger when crawling through a hole than LPS1175, LPS2081 and PAS, while the LPS1270 standard tests for hand holes as well. The tester can only use the rubber hammer on certain tools and into existing gaps, saws can only be used in exposed hinges, the scaffold pole can only be used on grilles so not against windows. The only impact test on glass is dynamic loading but that does not test impacts with tools that might smash or cut a hole or burst the glass out of the rebates or simply ram the glass out through the inside rebates taking them with it. It gets worse: RC1 does not require laminated glass, RC2 allows P4A safety glass, RC3 makes do with P5A safety glass – which needs to stop a crowbar for 5 minutes but is only tested with a metal ball and which LPCB say is not even SR2, RC4 fobs you off with P6B which would need to stop a hammer for 10 mins but is only tested against 30 axe blows and would not even stop a screwdriver, RC5 assumes P7B will stop an angle grinder but is only tested against 51 axe blows, and RC6 says P8B will see off a percussion drill but is only tested against 71 axe blows. Check ESG’s ‘just how tough is security glass’ video of these European standards like 30mm P8B going down with almost the first punch, against a sledgehammer anyway. Even if you specify locks and glazing which you know is more secure than what EN1627 requires, the RC rating does not test it all as one door.
  • LPCB say for glazed products RC1 is equivalent to at most SRA, RC2 varies from SRA through SRB to SR1 but probably just SRA, RC3 is a slight improvement varying from SRA to SR1, RC4 varies from SRA to SR2 but usually SR1, then there is a big step up to RC5 which varies from SR1 to SR5 but usually SR2 to SR4, RC6 varies from SR2 to SR6 but usually SR3 to SR5. Assuming you get appropriate locks and glazing then you probably need a RC5 to equate to an SR3. The twist is that EN1627 RC4 requires a 8.5″ brick wall so implies it is equal to it and if you only have a cavity wall or lightweight blocks then there may be little point having a window stronger than RC3, which is awkward as that pegs a brick wall at about SR1. You can see from the tool groups that RC4 is similar to SR3, and the standard even attacks for twice the time, so is not to be sniffed at, but the methodology has flaws including that it is hard to check UK accreditation, hardware is not tested in the product and testers are limited in how they are allowed to use tools. LPCB published a comparison of LPS1175 and EN1627.
  • In short, go for RC5 (Selzer S2es or RappBomek Stalprofil) if you want an almost affordable residential looking window that might well be as strong as your wall and do not paying for unnecessary armour against power tools or being left uncertain if it would survive a sledgehammer or pickaxe, but to replicate SR3 for high risk domestic risk or any kind of targeted attack you probably need RC6 glazed – which are hard to come by if you want residential style, in fact the author has yet to find any sold in the UK – RC3 & RC4 (RvE) is much more common on the continent and RC5 is about as high as it goes. Even then you need to ensure it is overspecified for dynamic impact as a proxy for attack on beads via glass and consider upgrading the glass to something you know is about as strong as the frame against your threat tools, like going from 9.5mm P6B to 20mm SR3 poly glass but that still leaves you not knowing if the bead can hold your thicker glass as it would never have been tested, except to the extent that it used thick laminated glass up to P8B which you replace with similar thickness but stronger poly glass. Either way, you are effectively buying a largely overspecified safe door rated against power tools that few will have after SHTF yet not rated against heavy hand tools found in LPS1175 or USA mob standards. If economic sense matters then unless your home is made of wood, breeze block or thin brick you may as well forget about EN1627 for now, unless you are happy to back up an RC4 with a shutter or grille. As these high threat level windows are ruinously expensive, horrendously ugly and probably overspecified by tool group for your needs, you are probably better off buying an RC4 with a mob attack accreditation such as FE5 to give assurance against sledgehammers and crowbars, in fact even RC3 doors can also come with that rating even though they don’t have an EN1627 rating against even a lump hammer.

• EN356
  • The accompanying standard to EN1627 for windows is EN356 for glazing, rated from P1A to P8B.
  • Glazing up to P5A weighs 16-22kg/m2 and is safety glass to stop 4.11kg 100mm diameter steel balls coming through accidentally after 3 strikes (9 for P5A) from 1.5-9m high and only needs glass 6.8mm-10.3mm thick so is not even anti bandit glass – which would be more like 11.5mm. P6B to P8B needs laminated glass 15-26mm thick weighing 23-30kg/m2 or polycarbonate laminated glass 10-18mm thick, as the test uses a mechanical sledgehammer and axe and 31-71 strikes to try and chop a 40cm x 40cm hole.
  • EN356 is even worse than EN1627. Even its top rating of P8B, which typically needs 26mm laminated glass or 18mm poly glass, is weaker than most homes’ walls. Laminated glass to EN356 does particularly badly against hammers. For example, two blows from a sledgehammer make a hand hole in P4A laminated glass, four blows of a lump hammer makes a hand hole in P5A laminated glass, P6B laminated glass allows a handle manipulation hole with a hammer and screwdriver in 6s and 19mm P6B laminated glass lets the back of an axe make a hand hole in 7s, while 30mm P8B laminated glass allows a hand hole from a sledgehammer (a SR4 tool) within 3s. In contrast you would not make a handhole in a brick wall with a sledgehammer in 3s, so even the thickest P8B glass usually leaves a weak spot. In case you have weaker walls than brick it is worth knowing that polycarbonate interlayers or spall liners make a huge difference, including in thinness so might be able to match such a wall in P8B glass. To be fair, you would ignore the safety grades of P1A-P5A as they are weaker than the now discredited 11.5mm anti bandit laminated glass. Only grades P6B-P8B are pretending to be security glass.
  • You probably want to go for LPS1270 security glazing which is rated to match LPS1175 SR levels and measures how many minutes it will stop a finger hole, hand hole and body hole. A good P8B glass could get you SR1 or at least LPS1270 001, but to match SR2 or SR3 you need 18-20mm poly glass, taking you beyond the scope of EN356. To use an EN1627 window (which only requires EN356 glazing) you probably need to upgrade the glass.
  • Research has found that P5A at most equates to SR1.
• You might come across the international version of EN356, ISO 16936.
• There are also what one might call USA ‘mob’ standards designed for embassies or prisons: SD-STD.01.01, ASTM F3038, ASTM F1915, ASTM F1233, HPW TP-0500.02 and WMFL. Whilst all those except the first two do not make promises about burglary tools, they do indicate that anything like a 20mm glass containing some polycarbonate – that you might use for manual attack standard such as LPS1270 SR2 or SR3 to match your wall – would give you one of the highest detention glazing forced entry ratings for a much longer attack by sledgehammer: in fact several times longer than most house walls would last. In reality, an intruder may guess that they would get in quicker by smashing out the wall fixings by hitting either frame or the bricks holding it, but these American standards would be great against hungry neighbours coming at you with fire extinguishers and sawn off chair legs. These standards have maximum grade strengths in ascending order of ASTM F1915, ASTM F1233 and either HPW TP-0500 or WMFL depending whether you want ballistic test as well to upgrade from forced entry to enhanced forced entry by softening up the glass with bullets first (rather than stopping them).
• Especially if in a glazed door, you sometimes find glazing in certified barriers to USA diplomatic standard SD-STD.01.01.
  • This rates for mob hand tool manual attack and/or rifle (M80 7.62 ball 823 m/s + M193 5.56 ball 986 m/s + M855 5.56 ball 899 m/s) at 20′ for 5, 15 or 60 minutes, with ballistic tested first. Government sometimes gets excited about how strong a product is as a potential embassy solution so tests to failure.
  • Products are tested with 6mm clearance around them in the frame. The assumption is that the products will be installed in steel or concrete, and a 12mm steel test rig is normally required.
  • Doors must be openable with only 5.5kg force.
  • Up to six shots can be fired in the middle of glazing at least 4″ apart. Opaque materials such as frames can be shot at least 1.5″ apart. Each component (eg lock, hinge) gets one shot.
  • A team of one, two, four or six fit young men attack at once depending on with which tool, trying to break through or disengage a lock. When testing glazing the wood axe can only be used in the last five minutes and the wood splitting maul cannot be used. The test fails if mounting hardware fails or a 12″ x 12″ x 8″ rectangular shape or 12″ x 12″ cylinder can pass through.
  • For FE5 rating two men attack with tools including a 10lb sledgehammer, 3lb carpenter hammer, 120lb ram with 4″x4″ face, 4′ crowbar, wood splitting wedge, 14″ end nippers, 1″ cold chisel, 0.75″ cold chisel, 2.25″ masonry chisel, 10″ Channellock wrench, 12″ vice grip, wooden broom. Against glazing, testers are presumably likely to favour the sledgehammer, ram, crowbar, and chisels with hammer as a knife. FE5 is similar in strength to an SR3 and slightly stronger than an RC3, although may be vulnerable to different toolsets, in particular it does not test an axe, drill, saw, plate shears, freeze spray or propane torch like SR3 has (even SR2 has plate shears) – this would seem to be a particular risk to polycarbonate like Hammerglass.
  • For FE15 rating six men attack with the same tools from FE5 with the addition of a 12lb sledgehammer, 3.5lb wood axe, 5′ crowbar, 2′ crowbar, 4′ boltcutter, 10″ screwdrivers, 10 & 15″ adjustable wrenches, 3/4″ & 1″ punches. The axe, screwdrivers and punches are a more reliable test of glazing as axes are used in LPS1175 and EN1627 for cutting out a man hole and screwdrivers and punches are used to make the initial hole before cutting or for manipulation of locks. FE15 is slightly stronger than an RC4 and about as strong as a LPS1175 C10, but again vulnerable to different toolsets, especially where it excludes the drill, saw, freeze spray and propane torch that SR3 has.
  • FE60 is simply FE15 extended another 45 minutes.
  • SD-STD.01.01 FE ratings are equivalent to UFC low threat.
  • SR4 is where the standard diverge quickly as SD-STD.01.01 does not use power tools such as SR4’s 12V drill, grinder and jigsaw now does it have a hole saw. You would best describe SD-STD.01.01 ratings as being close to LPS1175 C5, C15 & C60. The issue with SD-STD-01.01 for householders is that it exceeds the strength of a brick wall without protecting against severe tools, so is mainly only suitable for reinforced masonry buildings where only brute force is expected. However, some FE5s & FE15s come with other accreditations like RC3 or RC4, giving at least some protection against a wider toolset and thus more suited to maintain consistent protection across the facade of a reinforced masonry building. The reason why SD-STD.01.01 products do not come dual certified any higher than RC4 would be that RC5 upwards uses power tools, but that is not to say they could not take a long beating from hand tools on hand tools from RC3 or RC4 tool groups, although cutting could still be a risk. This might also come with options for wood finish or bullet resistant glazing where the product is doubling up for a more residential market given the EN1627 accreditation.

• ASTM F3038 is similar to FEBR above, using a six man team for 5, 15, 30 or 60 minutes, simulating a spontaneous mob using makeshift weapons. F3038 60 could survive 2,400 sledgehammer blows. It differs from SD-STD.01.01 in that it uses six men for all attacks and does not have a ballistic option. Based on team size this is most formidable mob forced entry standard, likewise for skilled attackers with tools up to about SR3.
• ASTM F1915 is USA prison forced exit standard.
  • It tests equally with blunt and sharp impacts with half the blunt impacts first then all the sharp impacts then the last half of the blunt impacts, rating from grade 4 for 10 minutes and 100 impacts, through grade 3 for 20 minutes and 200 impacts, grade 2 for 40 minutes and 400 impacts, to grade 1 for 60 minutes and 600 impacts.
  • ‘600 impacts’ means grade 1.
  • It is similar to EN356 as it uses an automatic hammer and axe.
  • A grade:
    • 4 roughly equals an ASTM F1233 II or HPW I or at least an HPW I
    • 3 roughly equals an HPW II or ASTM F1233 III or WMFL III
    • 2 roughly equals at least a WMFL III or HPW II
    • 1 roughly equals an ASTM F1233 IV or at least an HPW III or WMFL II
  • Typical rated products include:
    • grade 4 = 14mm poly glass / 12mm poly
    • grade 3 = 17mm poly glass / 10mm lam poly
    • grade 2 = 19mm poly glass / 12mm lam poly
    • grade 1 = 25mm poly glass / 19mm lam poly
• ASTM F1233 is a USA forced entry standard (with ballistic options) with increasing grades from class 1 to 5, with similar tests to HPW.
  • It is slightly shorter and class 1 only tests with a hammer so is a lower grade than available from the other standards. Scaffold pole, battering ram chisel and angle iron do not kick in until class 3, axe and wood splitting maul do not come in until class 4, the fire extinguisher is not repeated and only starts at class 2, there is no acetylene torch and screenwash, and there is no equivalent to HPW level V.
  • Grades are awarded by decimal codes indicating how far the product survived into the sequences with 1.5 being a full pass at grade 1, 2.8 being a full pass at grade 2, 3.10 being a full pass at grade 3, 4.13 being a full pass at grade 4 and 5.0 being grade 5 which is the addition of a 25 blows of a wood splitting maul to grade 4.
  • ’41 sequences’ means it survived all 41 sequences and thus scored grade 5.
  • A class:
    • 2 roughly equals an HPW level I or ASTM F1915 4,
    • 3 roughly equals an HPW level II or at least an WMFL 3 or ASTM F1915 3,
    • 4 roughly equals an ASTM F1915 grade 1 or 2 or HPW III or UFC very low threat, and
    • 5 roughly equals UFC low threat or WMFL 1 or at least HPW IV.
  • Body penetration is measured by passing a 9″ x 8″ x 5″ block. Contraband passing (relevant to preventing tools interfering with locks is deemed at 1/8″).
  • Typical glazing thicknesses with F1233 ratings are:
    • class 1 = 11.5mm poly glass
    • class 2 = 12mm poly
    • class 3 = 10mm lam poly
    • class 4 = 19mm lam poly
    • class 5 = 25mm lam poly

• HPW TP-0500.02 is a USA prison forced entry standard (with ballistic options).
  • It has ratings from level 1 to 5 based on how many of the 54 potential sequences are accumulated from working through each increasing level’s cycle of attacks with various tools, so ’54 sequences’ means level V.
  • Like WMFL, it uses blunt, sharp and thermal attacks, but at level 2 and above it adds chemical attacks.
  • Although there is some escalation of tool severity most increment in levels is by repeated cycles, so it measures how long it survives more than what it survives.
  • Its levels ranks as US DoD very low (levels II-III) to low (levels IV-V) threat level.
  • Level:
    • I roughly equates to at most ASTM F1915 4
    • II roughly equates to ASTM F1915 3 or WMFL III
    • III roughly equates to ASTM F1915 2 or at least WMFL III
    • IV roughly equates to ASTM F1915 1 or WMFL II
  • Every test starts at:
    • level I with 50 blows of a sledgehammer on wedges and 50 blows on scaffold poles and a minute of fire extinguisher (eg 11mm poly glass / 12mm poly);
    • level II lasts twice as long again and gets a battering ram, another 50 wedge attacks, 25 more scaffold pole strikes, 25 doses of sledgehammer on angle iron, 25 thumps of hammer and chisel, 25 swings from a wood maul, another fire extinguisher session, a propane torch, washed down with half a pint of petrol (eg 17mm poly glass / 10mm lam poly);
    • level III lasts about as long as level II involved getting wedged another 75 times, scaffold poled another 25 times, angled ironed another 25 times, rammed again, 50 more strikes of hammer and chisel, another 25 beatings with the wood maul, another blast of propane torch and half a pint of screenwash (eg 19mm poly glass / 19mm lam poly);
    • level IV lasts a fair bit longer than level II and adds a rerun of level III plus an extra 25 chisel hammerings and half a pint of acetone but replaces 25 angle iron blows with 25 fire axe chops (eg 25mm poly glass / 25mm lam poly);
    • level V lasts as long as level I and II combined and adds a rerun of level IV plus an extra 50 wedge hammering, an extra 25 wood axeings, an extra 25 wood maulings, and replaces the propane torch with an acetylene torch, but drops the screenwash and 25 of the chisel hammerings (31mm lam poly).
• WMFL is a USA ballistic, forced entry & thermal attack standard (relying largely on brute force and ignorance) rating from:
  • level III for 30 mins manual attack with 2lb hammer, 4lb hammer, 10lb sledgehammer, cold chisel, propane burner and fire extinguisher (eg 19mm poly glass / 10mm lam poly) = roughly equal to ASTM F1915 3 or at least ASTM F1233 3 or HPW III, through
  • level II for 60 mins manual attack with level III tools plus scaffold pole, rebar, chair leg, and 10″ long 0.25″ thick knife (22mm poly glass / 12mm lam poly) = at least equal to at least ASTM F1915 2 or HPW II or at most ASTM F1233 3, to
  • level I for level II plus ballistic with 25 rounds from a 240 grain .44 magnum (eg 32mm poly glass / 31mm lam poly) = roughly equates to HPW V or at least ASTM F1915 1 or at most ASTM F1233 V.
  • There is also the domestic window security standard ASTM E2395 which tests a hammer and hurricane missile.
• The USA DoD navy security glazing handbook specification for forced entry glazing is that glazing cannot provide high threat protection, and.
  • For low risk (smash and grab) use 6mm laminated strengthened glass.
  • For medium risk (noise, big tools, multiple blows) use glazing to forced entry standards according to threat as strong as the wall would be without reinforcement, with:
    • 6mm steel frame,
    • 5mm steel beading with 25mm bite and 32mm rabbet depth fixed with at least 2 10mm shouldered bolts per side on 18” centres within 9” of corners,
    • maximum 110cm glazing span between members,
    • bolts embedded 76mm.
  • For low threat (light hand tools):
    • fixed with 9mm lag bolt at 18” centres and within 9” of corners,
    • fixed to wall of:
      • wood (1” tongue and groove on 0.75” plywood),
      • 6” reinforced grouted concrete block, or
      • 4” reinforced concrete.
    • glazing of:
      • Insulated unit of 6mm laminated annealed glass – 6mm air gap – 6mm polycarbonate,
      • 5mm annealed glass – 13mm extruded ionomer – 5mm annealed glass,
      • 5mm annealed glass – 10mm polycarbonate – 5mm annealed glass, or
      • 10mm polycarbonate
  • For medium threat (heavy hand tools, battery tools):
    • fixed with 0.5” one piece expansion sleeve or 10mm taper bolt, at 12” centres and within 6” of corners,
    • fixed to wall of:
      • 8” reinforced grouted concrete block, or
      • 6” reinforced concrete.
    • Glazing of:
      • Insulated unit of 6mm laminated annealed glass – 6mm air gap – 28mm laminated polycarbonate,
      • 22mm laminated annealed glass – 25mm extruded ionomer – 4mm annealed glass,
      • 5mm strengthened glass – 6mm annealed glass – 9mm polycarbonate, or
      • 32mm laminated polycarbonate
• The USA DoD navy physical security design handbook says that:
  • For one minute against low threat light hand tools in a wood frame wall (which is their only example of less than concrete) you need a frame with 6mm thickness and 6mm beading thickness with 25.4mm bite and 32mm rabbet depth, fixed with 9.5mm thick lad bolts embedded 90mm, and:
    • 12.7mm polycarbonate,
    • 17.4mm polycarbonate glass including 9.5mm polycarbonate,
    • 22.2mm ionomer glass including 12.7mm core, or
    • 35mm insulated unit of 12.7mm polycarbonate and 6.4mm laminated glass.
  • For four minutes against medium threat heavy hand tools and battery tools in a medium risk concrete block wall you need a frame with 6mm thickness and 6mm beading thickness with 25.4mm bite and 32mm rabbet depth, fixed with a 10.7mm thick one piece expansion sleeve embedded 100mm or 9.5mm taper bolt embedded 75mm, and:
    • 32mm laminated polycarbonate,
    • 24mm polycarbonate glass including 12.7mm polycarbonate,
    • 44mm insulated unit of glass – air gap – 32mm laminated polycarbonate, or
    • 54mm ionomer glass including 25mm extruded ionomer.
  • For fifteen minutes against high threat power tools you need to combine a window with a sliding panel bolted to the inside of the wall.
• The takeaways for home invasion are that 0.5” polycarbonate will give good blast resistance unless someone targets your building and it will delay hand tools similar to SR3 but does not help with ballistic threats. Upgrading to 1” stops a 9mm handgun which is a big jump in cost to swallow unless you expect guns. Upgrading to 1.25”polycarbonate glass stops a .44 magnum or shotgun and delays battery tools, so covers all the classic SHTF risks, but is not only expensive but may be stronger in a blast than the wall so cause a partial collapse, and may be more than you need against manual attack too, as it stops more battery tools than SR3 requires, in fact it would delay sledgehammers and safecracker battery tools, so again you may need a new wall to go with it. As 12-22mm polycarbonate glass gets SR3 manual attack rating and EXV25 to EXV15 blast rating, that is more likely to be proportionate choice and then back it up with ballistic screens on the ground floor in times of tension.
• Since the 1993 edition the US UFC security specification has said you can get 5 minutes delay against level IV from commercially available windows. The 2020 edition specification is:
  • Level II – low threat:
    • 1 minute delay from low threat needs frame of ¼” steel with 3/16” beading with 1” bite, 1.25” rabbet and fixed with shouldered 10mm bolts 2 per side & on maximum 18” centres and within 9” of corners, maximum 42” space between frame members, fixed with 10mm bolts embedded 75mm on maximum 18” centres and within 9” of corners, assuming wood frame wall, and:
      • Double glazed: 0.25” laminated annealed glass, ¼” air gap, 0.5” polycarbonate,
      • Ionomer: 3/16” annealed glass, 0.5” extruded ionomer, 1/8” annealed glass,
      • Polycarbonate glass: 3/16” annealed glass, 3/8” polycarbonate, 3/16” annealed glass,
      • Polycarbonate: 3/8” polycarbonate,
      • 0.25” wired glass,
      • 0.25” tempered glass (beware glass breakers),
      • 0.5” acrylic,
    • 2 minutes from 0.25” plate glass with 10 gauge (3.1mm) 6”x6” steel mesh cover,
    • 2 minutes from 0.25” laminated glass in aluminium frame,
    • 2 minutes from 9/16” laminated glass in aluminium frame.
  • Level III – medium threat:
    • 4 minutes delay from frame of ¼” steel with 3/16” beading with 1” bite, 1.25” rabbet and fixed with shouldered 10mm bolts 2 per side & on maximum 18” centres and within 9” of corners, maximum 42” space between frame members, fixed with 0.5” once piece expansion sleeve or 3/8” taper bolts embedded 75mm on maximum 12” centres and within 6” of corners, assuming grouted concrete blocks or reinforced concrete wall, and:
      • 1 minute (3 mins level II) from 0.5” polycarbonate,
      • 1 minute (also level II) from 0.25” acrylic in aluminium frame,
      • Double glazed: ¼” laminated annealed glass, 1.4” air gap, 1.125” laminated polycarbonate,
      • Ionomer: 7/8” laminated annealed glass, 1” extruded ionomer, 3/32” annealed glass,
      • Polycarbonate glass: 3/16” strengthened glass, ¼” annealed glass, 3/8” polycarbonate,
      • Polycarbonate: 1.25” laminated polycarbonate,
    • 5 minutes from 0.25” plate glass with ½” A36 steel bars each way on 6” centres.
  • Level IV – high threat: there are only a few products at this protection level.
    • 1 minute (also levels II-III) from 11/16” glass-clad polycarbonate glass including 3/8” polycarbonate core,
    • 5 minutes (also level III & 15 mins level II) from 13/16” glass-clad polycarbonate glass including 0.5” polycarbonate core.
  • Level V – very high threat: at this protection level you would have to make your own window, but windows are advised against or should be less than 96 square inches or maximum 6” slits and would then need to be protected by screens or shutters.
  • For extra delay, add steel bar matrix with welded intersections, bolted in steel frame or ideally cast in situ. This needs a concrete wall as brick is quicker to cut than bars.
    • 1 minute at level II from 3/8” on 3” centres,
    • 1 minute at level III from ½” on 4.5” centres,
    • 1 minute (also 5 mins at level II) from 3/8” hardened steel bars on 4” vertical centres & 8”horizontal centres,
    • 1 minute (also 5 mins at level III) at level IV from 3/8” hardened steel bars on 4” vertical centres and 8” horizontal centres,
    • 1 minute at levels II & III from 0.5” A36 steel bars on 4” vertical & 8” horizontal centres,
    • 2 minutes at levels II & III from 0.5” A36 steel bars on 4” vertical centres with 3/8”x1.25” or 1/8” x 1.5” A36 steel bars on 8” horizontal centres,
    • 2 minutes (also 5 mins at level III) at level IV from 1/2” hardened steel bars on 4” vertical centres & 8” horizontal centres,
    • 2 minutes at level IV from 5/8” on 3” centres,
    • 2 minutes at level IV from ¾” on 4.5” centres,
    • 2 minutes (also 4 mins at level III) at level IV from ½” hardened steel bars on 6” centres,
    • 3 minutes at level II for 22 gauge (0.7mm) sheet metal duct with steel bars each way on 6” centres (also gives 1 minute against level V explosives) (Krueger 91310 is such a prison ventilation grille),
    • 4 minutes at level III from 0.5” A36 steel bars each way on 6” centres,
    • 5 minutes at level III from 7/8” A36 steel bars on 4” vertical centres with 3/8”x2.25” A36 steel bars on 8” horizontal centres,
    • 6 minutes at level III from no5 steel wire each way on ¾” centres,
    • 6 minutes at level III from no8 steel wire each way on 5/8” centres,
    • 7 minutes at level III from 7/8” hardened steel bars on 4” vertical centres with 3/8”x2.25” hardened steel bars on 8” horizontal centres,
    • 8 minutes at level III from 3/8” A36 steel bars each way on 1.25” centres,
    • 9 minutes (21 mins at level II) at level III from ½” A36 steel bars each way on 2.25” centres,
    • 15 minutes (also 7 mins level III) at level II from 0.25” A36 steel bars each way on 1.25” centres,
    • Level II protection ought not to need bars but it is easily done.
    • Level III protection is ideally suited to bars in technical terms.
    • Level IV protection cannot be achieved strictly speaking with conventional bars but it can be done for a shorter time or by beefing up thicknesses to over 16mm.
    • Level V needs sacrificial enclosing structures.
  • Frames should be steel 50mm sections with external stops integral or welded and internal stops high strength alloy machine screwed with anti tamper heads.
• The 2020 version of US military specification for security windows still claims that windows can only achieve protection level II – which is 1 minute against low threat tools (small hand tools), and that grilles or shutters are needed to achieve protection level III or IV (4 or 5 minutes or 15 minutes) against medium (battery) or high threat (thermal and power) tools. However, it has been updated with glazing options to get up to full level III protection for 5 minutes with polycarbonate glass, and even up to level IV protection albeit for shorter delays of 1-5 minutes.
• Sandia research from the 1970s for nuclear safety says:
  • 1/8″ glass lasts 30s against a hammer. If protected by a steel rod to turn a man sized pane into effectively multiple 6″ wide panes it lasts 36s against a hammer and cutting torch.
  • Riveted exmesh covered sash window with less than man size panes of 1/8″ glass lasts 1m against a 5lb crowbar.
• Different manual attack standards assume different toolsets and working times, but based on rough order of dangerousness of tools to glazing, working times and energy levels the ranking of manual attack glazing in ascending order of strength is:
  1. ASTM F1233 classes 1-3
  2. UFC very low threat
  3. SBD / PAS 24
  4. P1A (170J accumulated)
  5. NIJ 0316.00-80
  6. P2A (360J accumulated)
  7. ASTM F1233 4
  8. HPW TP-0500.02 II-III
  9. P3A (720J accumulated)
  10. P4A (1,080J accumulated) / RC2
  11. P5A (3,240J accumulated) / RC3
  12. SRA / STS 204
  13. SRB
  14. P6B (14,850J accumulated ) / RC4
  15. P7B (17,400J accumulated) / UL972)
  16. ASTM F1915 4
  17. P8B (25,200J accumulated) / SR1 / LPS1270 001
  18. HPW TP-0502.02 IV-V
  19. SD-STD.01.01
  20. ASTM F1233 V
  21. ASTM F1915 3
  22. ASTM F1233 II / HPW TP-0500.02 I
  23. ASTM F1233 1.4 CP & 2.0 BP / HPW TP-0500.02 I
  24. ASTM F1233 III / WMFL III
  25. SR2
  26. LPS1270 012
  27. LPS1270 112
  28. RC5
  29. SR3
  30. LPS1270 013
  31. LPS1270 123
  32. LPS1270 223
  33. ASTM 1915 2 / HPW TP-0500.02 II / WMFL II
  34. ASTM F1233 1.5 CP & 3.2 BP
  35. ASTM F1233 IV / ASTM 1915 1 / HPW TP-0500.02 III
  36. ASTM F1233 2.4 CP & 3.5 BP
  37. ASTM F1233 5 / HPW TP-0500.02 IV
  38. HPW TP-0500.02 IV / ASTM F1233 2.4 CP & 5 BP / ASTM F1915 1
  39. WMFL 1 / ASTM 1915 1 / HPW TP-0500.02 IV & V / ASTM F 1233 5BP 2.5C
  40. SR4
  41. LPS1270 224
  42. LPS1270 234
  43. RC6
  44. SR5
  45. LSP1270 235
  46. SR6
  47. LPS1270 246

Products

• Your options for typical domestic security are:
  1. Stick to LPS1175 for UK assurance on the whole product by using Hampton (and Sash Window Conservation if you can use a sash) and seeing if Crittal are prepared to have a conversation with you despite you not running a prison. Either way, unless you get a Crittal SR3, with only SR2 rating your product may need backing up with a blind, shutter, grille or maybe even secondary glazing to buy time against chopping, drilling or burning with toolset C such as an axe, crowbar, chisel, battery drill or blowtorch. This is an oligopoly with only three suppliers so is not going to end well for your wallet. You would probably either go for a Hampton to SR2 and maybe back it up with another product, or if your wall is beefy enough use a Selectaglaze secondary window to SR3 with options to go further on blast and ballistic.
  2. Gamble on the credibility and relative weakness of an EN1627 rating from the EU for the whole product rated RC4 upwards in the hope of slightly more suppliers to shop around with. Many manufacturers go up to RC3 but not so many RC4 so these will not be cheap either. They are more likely to need backing up to protect glazing or the product in general against multiple noisy tools, perhaps thicker glazing, secondary glazing or grille or shutter. However, if your threat is a hungry mob rather than professional burglar then you may decide to go for cheap brawn of a European rating assuming you can validate it somehow.
  3. Make do with an easier to find cheaper RC3 product, try to upgrade the glazing, and almost certainly reinforce it with shutter, grille or secondary glazing.
• The problem with reinforcing residential windows via blinds, grills, shutters and secondary glazing in the average home is you are forced to face fix or screw into breeze block meaning the extra security might simply be punched out in one piece, plus there is the inconvenience of losing discretion from the street and your windowsill and having to open one product before the other.
• Vision panels are available, which are normally small to go in doors, but a few are available in fixed light window sizes like cell windows. LPS1175 door manufacturers incorporating them mostly use 45mm laminated glass for SR2-3 and Tecdur LPS1270 poly glass for SR4 upwards and Tecdur GridGlass for SR5-6, but other options include Surelock McGill (mesh for SR4 upwards) or Vistamatic vision panels, while other products rely on bars from SR3 upwards. Glazing is usually overspecified compared to LPS1175 bodily entry and its corresponding LPS1270 glazing due to simplicity of using one product for multiple SR ratings and fear of fixings or handles being attacked through a tool or hand hole.
• LPS1175 windows are available from:
  • Crittal Fendor have approval for their Secureline windows rated SR2 to SR4, up to SR3 with top hung opening lights, and specialise in bar-less composite prison windows.
  • Hampton Conservatories have two products of interest:
    • The SR2 Sapele mahogany 58mm or 42mm rebate width fixed light casement windows which can also be rated EN1063 BR2 against low power rifles and 9mm handguns. Security glazing options with product codes for 17mm / 22mm / 33mm / 39mm / 43mm / 70mm glazing bar widths, frame thicknesses of 105mm or 92mm and window thicknesses of 70mm or 57mm are:
      • 12mm single (SSec92/57 1 & SSec92/57 2),
      • 14mm single (SSec92/57 3 & SSec92/57 4),
      • 20mm single (SSec92/57 5 & SSec92/57 6),
      • 40mm single (SSec105/70 10 & SSec 92/70 10),
      • 24mm double 12-8-4 (SSec92/57 7 & SSec92/57 8),
      • 24mm double 14-6-4 (SSec92/57 9 & SSec92/57 10),
      • 38mm double 20-14-4 (SSec105/70 1, SSec105/70 7, SSec92/70 1, SSec92/70 4 & SSec92/70 7),
      • 38.4mm double 20-12-6.4 (SSec105/70 3, SSec105/70 4, SSec105/70 8, SSec92/70 2, SSec92/70 5 & SSec92/70 8),
      • 40mm triple 12-10-4-10-4 (SSec105/70 5, SSec105/70 6, SSec105/70 9, SSec92/70 3, SSec92/70 6 & SSec92/70 9).
    • Their other SR2 is the Quattroglide vertical wooden sliding sash with glazing thicknesses of 20mm/40mm single glazed, or 20mm + 6.4mm with 12mm gap or 20mm + 4mm with 14mm gap double glazed (they also seem to claim to have a double glazed SR2 with 24mm rebate width and even an SR2 BR2 with 20mm rebate width and even an SR2 with a 14mm or 12mm rebate width) or a 40mm rebate triple glazed. Quattroglide can take SR2 glazing with 20mm, 14mm or 12mm attack faces in these formats with glazing bar widths or 17mm / 22mm / 33mm, window thicknesses of 70mm or 57mm and frame thicknesses of (200mm or) 174mm:
      • 40mm single (Sec29 & Sec30, also to BR2),
      • 20mm single (Sec5 & Sec6, also to BR2),
      • 14mm single (Sec3 & Sec4),
      • 12mm single (Sec2),
      • 38.4mm double (Sec13, Sec14, Sec19, Sec20, Sec25 & Sec26, also to BR2),
      • 38mm double (Sec24),
      • 38mm double (Sec11, Sec12, Sec17, Sec 18 & Sec23, also to BR2),
      • 24mm double (Sec7, Sec8, Sec9, Sec10),
      • 40mm triple (Sec27 & Sec28),
      • 40mm triple (Sec15, Sec16, Sec21 & Sec22).
  • PremierSSL sell the Jansen Facade curtain wall to SR3 which could can be used as a fixed light.
  • R & D Sheetmetal do Secureview windows rated SR2 to SR5 although these are actually bolt-in vision panels for their Evo security doors.
  • Sash Window Conservation do a Sash Secure 240 Embassy wooden vertical sash to SR2 and BR2 for bullet resistance. It can be bonded to the wall for some blast resistance.
  • Selectaglaze only do blast resistant aluminium secondary glazing with up to 12mm polycarbonate glass and offer sashes, casements (up to 24mm sealed unit option) and demountable fixed lights, including in SR1 (12mm laminated glass) to SR2 (12mm polycarbonate glass), and demountable fixed lights, including in SR3 using 12mm Tecdur, with woodgrain effect option. These could be handy for backing up existing or new windows, even security windows, to buy more time against toolset B, although cannot stop toolset C if you want an opening version.
    • Their SR3 S55DFL demountable fixed light also offers FB4 ballistic rating with 22mm glazing, steel reinforcement and trickle ventilation, and has a minimum size of 400x400mm.
    • They also do the S43 fixed panel to SR3 and EXV25 but not ballistic, they claim with only 12mm Tecdur, although normally their 12mm rebate only takes them up to SR2 – with their 22mm rebate being reserved for SR3.
    • Their Tecdur options put polycarbonate on the attack face, creating a weathering problem, although for the SR2 – but not SR3 – they can switch it to a glass-polycarbonate-glass sandwich.
    • Their Series 42 fixed ballistic, 55DFL blast or ballistic, 95 vertical slider blast, 85 horizontal slider blast, 41 casement ballistic, 43 DFL ballistic and 50 casement blast models are SBD terror rated.
    • They have a video clip of their S43 Heavy Duty Security fixed demountable secondary glazing demonstrated with a sledgehammer and axe from tool group D. It is not clear what glazing it has since it only takes up to 12.04mm glass but it can come in up to SR3 so probably 12mm Tecdur. They have not denied they cannot go in breeze block walls or bays.
    • The demountables are removed with putty knife, screwdriver and glass suckers, hence the importance of glazing strong enough to stop a hand hole.
    • The glazing is security taped but only on one side for the ballistic version which uses an attack face gasket.
    • Casements or sliders can treat a patio or French doors.
    • They do SBD versions using 6.8-11.5 laminated glass.
    • They suggest you might buy through their reseller ATAJ.
  • Global Security Glazing make Super Secur-Tem5 27mm laminated glass to UL972
  • Pilkington make Optilam laminated glass to:
    • P2A 6.8mm
    • P4A 9.5mm
    • P5A 10.3mm
    • P6B 11mm
    • P7B 22.6mm
    • P8B 39mm
  • Saint Gobain make European market glass to the lower EN356 standard, although it can be thick and ballistic:
    • Vetrotech Vetrogard laminated glass to:
      • P6B 15mm
      • P7B 22mm
      • P8B 27mm
    • Vetrogard Pro laminated glass combines ballistic & manual attack to:
      • P8B + BR4 S + SG1 S 35mm
      • P8B + BR3 NS 44mm
      • P8B + BR6 S + SG2 S 51mm
      • P8B + BR4 NS 54mm
    • Polygard poly glass:
      • P7B 15mm
      • P8B 17mm
    • Polygard pro poly glass combines ballistic & manual attack
      • P8B + BR4 NS + SG1 NS 21mm
      • P8B + BR6 NS + SG2 NS 38mm
    • The same group, Hamilton Erskine, make a UK product, Tecdur Secure Glass (‘TSG’) in laminated glass from P1A to P5A, laminated glass or poly glass from P6B to P8B/SR1 and poly glass from SR2 to SR6, which can all be upgraded to ballistic:
      • EN356 P1A 8.4mm lam glass
      • EN356 P2A 8.8mm lam glass
      • EN356 P3A 9.1mm lam glass
      • EN356 P4A 9.5mm lam glass
      • EN356 P5A 10.3mm lam glass
      • EN356 P6B 11mm lam glass
      • EN356 P6B 9.5mm poly glass
      • EN356 P7B 24mm lam glass
      • EN356 P7B 14mm poly glass
      • EN356 P8B 29mm lam glass
      • EN356 P8B + LPS1270 011/001 (SR1) 16mm poly glass
      • LPS1270 112 (SR2) 12mm poly glass
      • LPS1270 123 (SR3) 14mm poly glass
      • LPS1270 234 (SR4) 34mm poly glass
      • LPS1270 235 (SR5) + BR4 NS 40mm poly glass
      • LPS1270 246 (SR6) Grid Glass 51mm poly glass
  • Their 22mm ‘enhanced security glass’ is 6mm toughened glass + 2mm resin + 6mm poly + 2mm resin + 6mm toughened glass.
  • The 40mm Tecdur is favoured for remote sites with panic bars for its extended delay against fishing holes. Fabricators are known to overspecify from SR3 to SR4 for bodily entry in order to get three minute delays against fishing holes or five minute delays against hand holes. Grid Glass embeds a metal grille to further delay hand holes and bodily entry, which is not just for high risk sites but areas with slow response times. The SR2 & SR3 rated glass is thinner and lighter (19 & 22kg/m2) than the SR1 as it is single clad but with thicker poly, whereas the SR1 uses heavy but cheaper glass to take the brunt of basic tools. They are especially attractive as they have ratings showing they can demoralise intruders by delaying a tool hole for a minute and a hand hole for one or three minutes, whilst fitting in normal rebates and perhaps as a DGU for insulation and to protect the poly. Remember, though, that Tecdur is not rated for the axes and sledgehammers they show in their demo videos until it is 34mm thick, whereas they show short delays of about a minute by the 14mm SR3 product.
  • Stronghold sell Jansen steel residential windows rated RC3 which can be upgraded to ballistic and Schuco aluminium residential windows rated up to RC4 or to FB4 which can be upgraded to cover both. They also do a blast version to EXV19E that does not appear to allow manual attack and ballistic rating.

• Stafford Bridge Doors do SR rated steel fixed windows, the Durham SC05 and Catterick SC05 to SR3, FB4 & EXV15, and the Catterick SD10 to SR4, FB6 & EXV12, although these are really vision panels they can handle up to 6m²; it is not clear what combinations of threats can be protected in one product.
• Surelock McGill sell 17cm wide 17/37/67cm high steel bolt through multi threat cassette vision panels which can come as part of LPS1175 doors from SRB & SR2-6, FB2/4/6 and EX25/15 with mesh from SR4 upwards. Maximum length is 37cm at SR5-6 and even that is an upgrade. The original Teckentrup 62 SR-rated security doors use these.
• On the continent and through UK resellers or manufacturers adopting the standard there are EN1627 security windows:
  • RvE do RC4 oak doors and French casements and fixed lights with ballistic option.
  • Sommer do the Sokaltherm 78B+ custody window to RC3 with P7B glazing, customisable up to RC5.
  • RappBomek say they do 59mm doors and windows to RC5 with FB4 or FB7 using Stalprofil.
  • Salzer say they do blast & ballistic doors to RC6 (S4 & S4HS in steel, also to SD-STD.01-01), to RC4 in aluminium (S2es 135mm profile gives FB7, S6es 115mm profile gives FB4), and windows in aluminium to RC5 (plain S2es is possibly RC6, heritage S6es is RC4, Securon tilt windows are RC3 when open), and secondary glazing. Their S4W is a strongroom door to RC6 or EN1143 grade 1. Their S4T is an embassy door, rated to SD-STD-01.01, glazed to up to 15 minutes or flush to up to 60 minutes, with window options of 5 & 15 minutes.

• Blast & Ballistics also do security secondary glazing although with only glazing rated, up to P8B, using Saint-Gobain Stadip Protect.
• Skydas in Lithuania and effectively their UK successor Fort Engineering have been selling unrated (but probably amongst the strongest) fixed and operable (casement, sliding, sash, bay) security windows. Their sashes are stainless steel profiles covered in EDMDF with two FIAM locks and 11mm anti bandit laminated glass or 25mm ballistic which they said was FB4 to stop a 9mm bullet. From literature from Fort Engineering reseller Magnificent Security it appears there is a steel bifold that can probably be fitted with anti bandit glass.
• ESG make ESG Secure forced entry poly glass. Some thicknesses also come with ballistic ratings. The lineup is:
  • P2A 6.8mm
  • P3A 9.2mm
  • P4A 9.5mm
  • P5A 10.3mm
  • P7B + LPS 1270 001 11mm
  • P8B/P7B + LPS1270 001 + EN1063 BR1 13mm (they give both EN356 ratings)
  • P8B + LPS1270 112 + EN1063 BR2 18mm
  • P8B + LPS1270 123 + EN1063 BR2 20mm
  • P8B + LPS1270 223 31mm
  • P8B + LPS1270 224 + EN1063 BR4 39mm
  • P8B + LPS1270 234 42mm
  • P8B + LPS1270 235 + EN1063 BR5 57mm
• Global Security Glazing make poly, lam poly & poly glass forced entry glazing:
  • Laminated glass 27mm UL972
  • Secur-Tem poly glass:
    • 11mm HPW I
    • 14mm HPW I / ASTM 1915 4
    • 18mm HPW II / ASTM 1915 3
    • 19mm HPW III / ASTM 1915 2/ WMFL III
    • 21mm HPW II / WMFL III
    • 24mm HPW III / ASTM 1915 2 / WMFL II
    • 26mm HPW IV / ASTM 1915 1 / WMFL II
    • 32mm ASTM 1915 1 / WMFL I
  • Lexgard lam poly:
    • 10mm ASTM 1233 III / ASTM 1915 3 / HPW II / WMFL III
    • 13mm ASTM 1233 III / ASTM 1915 2 / HPW II / WMFL II
    • 19mm ASTM 1233 IV / ASTM 1915 1 / HPW III
    • 26mm ASTM 1233 V / HPW IV
    • 32mm ASTM 1233 V / ASTM 1915 1 / HPW V / WMFL I
  • Lexan poly monolithic 13mm to ASTM 1233 II / ASTM 1915 4 / HPW I
• Some Lexgard lam poly facts for manual attack:
  • the 2 ply 10mm MPC375 is rated to survive:
    • 20 mins (50 blunt impacts and 50 sharp impacts) of prison riot to ASTM 1915 grade 3,
    • 11 mins of attack plus propane torch, chisel, sledgehammer and petrol to ASTM F1233 class III,
    • sledgehammer & wedges, chisel & hammer, wood maul, extinguisher , acetylene torch and petrol to HP White level II-TP-0500.02, and
    • 30 mins (20 mins of 2lb hammer plus 10 mins of 10lb sledgehammer) of hammering to WMFL level III;
  • the 3 ply 13mm MPC500 does not help further against cutting or melting but doubles impact delay to 40 mins against a prison riot with 100 blunt and 100 sharp impacts to ASTM 1915 grade 2 and to 60 mins of hammering to WMFL level II (twice as strong as the same thickness of single ply Lexan);
  • the 3 ply 18mm RC750 upgrades you to last 60 mins against a prison riot with extra acetone, axe, sledgehammer and chisel & hammers blows to ASTM 1233 class 4 and with 60 mins of 300 blunt and 300 sharp impacts to ASTM 1915 grade 1 and with extra attacks and windscreen wash to HP White level II-TP-0500.0;
  • the 4 ply 25mm MP1000 upgrades you to resist longer attacks to ASTM 1233 class V and extra attacks and fire axe and acetone to HP White level IV-TP-0500.0,
  • the 4 ply 32mm SP1250 upgrades you to resist longer attacks to HP White Level V-TP-0500.02 and WMFL Level I (which is level II for 60 mins hammering + ballistic for .44 magnum 240 grain.
  • This suggests that if you are not expecting fancy tools like a drill and recip but just a mob attack then 10mm laminated poly is enough to give continuous strength compared to a brick wall.
  • Lexguard MP1000 (26mm) is not only UL752 level 2 ballistic but rated ASTM F1233 Class V & HP White Level IV- TP-0500.02 for manual attack and can see off several minutes of sledgehammer and axe, while MP1250 (32mm) is not only UL752 level 3 ballistic but rated ASTM F1233 Class V, ASTM 1915 Grade 1 (60 min prison riot) & HP White Level V- TP-0500.02 WMFL Level I for manual attack so stopping 300 sledgehammer blows and 300 axe blows is deemed to last an hour.
• The only CPNI rated windows are fixed panels:
  • Opaque fixed panels from Crittal Fendor (Cellguard 2 rated Base (c. SR3) and Cellguard 4 rated Enhanced), and
  • Fixed demountable aluminium secondary glazing from Selectaglaze (S55DFL, can include SR3, EN1522/3 FB4 ballistic and ISO16933 EXV25 & EXV15 blast with up to 22mm glazing).

Multi-threat

• Some multi-threat products have been mentioned above. Counter terror products often cover blast, ballistic and manual attack, while others just handle ballistic and manual attack. But what the author has never seen done before is defining how to balance the allied risks in one product, so let us have a go…
• …Firstly, as part of prepping you will have weighed up the risks by gauging what the impacts and chances are of the threats of intrusion, shooting or bombs and allocated them their share of your prepping budget. You might judge that all three impacts are the same: you and/or your preps get destroyed or stolen, so it is a near infinite impact, which multiplied by any slim chance of happening still warrants a big spend compared to other more likely but less painful scenarios like unemployment or flood. An economist would say ‘ask yourself what would you pay to allow somebody to crowbar, shoot or bomb their way in’? That is your budget cap even if you have more money than sense. Let us say you are an oligarch with a prepping budget of £1,000,000, and the impacts of crowbar, bullet and bomb are £10,000,000 each – as that is how you value your life, a total of £30,000,000, and all your other risks add up to a total impact of £10,000,000, as they are not lethal although there are a lot of them, perhaps 100 risks with impacts of £100,000 each. Your grand total impact is assumed to be £40,000,000 if no impacts duplicate anything – you can only be killed once and only lose the same job once even though there are several risks that can cause it. Your crowbar / bullet / bomb impact is 75% of your total prepping risks impact. It would get 75% of your prepping budget if all chances were the same, but they are not. Let us say your chance of disaster in your lifetime from a crowbar, bullet or bomb is 33.33% (perhaps 3.33% chance bomb in war, 5% bullet in SHTF and 25% crowbar for any house invasion). Meanwhile, the chance of one of the other risks crystallising is 66.67%. The ‘break-in’ impact is 75% but the chance is 33.33%, multiplying to 2,500. The ‘other’ impact is 25% but the chance is 66.67%, multiplying to 1,666.67. Add 2,500 to 1,666.67 equals 4,166.67. Divide 2,500 into 4,166.67 equals 60%. ‘Breakin’ should get 60% of your budget, or £600,000.
• Secondly, assuming you only want one window per wall opening to handle all three threats, you do not need to completely divide up budget between the three risks, just share out the product compromises between the risks in the right proportions. So, at 3.33% chance, blast resistance will almost certainly have to come as a by-product of the strength of the product that addresses ballistic and manual attack. And it is not looking good for the ballistic vision panel industry either, as at 5% chance bullets will probably have to be stopped by manual attack glass. Crowbar wins the day with 25% chance, so let us start with manual attack glass.
• Thirdly, the good news is that any glass strong enough to stop crowbars and bullets will stop a blast that does not knock the wall down. Unfortunately ballistic glass tends to be thicker than manual attack glass, so the question is which bullets do you need to stop? If your ballistic threat is severe you may have to divert any spare manual attack budget to upgrade it to cover a higher ballistic rating. This is probably possible except for the largest estates, as manual attack windows are not outrageously expensive, just expensive, in fact you would probably be buying heritage security windows and adding grilles, shutters or maybe even secondary glazing. In such a niche sector you may have to limit your ambitions at FB4 for ballistic based on width of rebates and certifications on the market, but even that might not solve everything as although some manual attack windows are also ballistic most are not blast rated – to get that you might have to resort to secondary glazing. But in reality you could judge for yourself that you will get more than enough blast rating from a sturdy FEBR window. What may happen in practice is you either to buy an expensive ugly industrial looking window certified for all three threats, or be glad that SR3-strength glass covers any blast that you do not need a bunker for so you just have to agonise over how much thicker to make the glass against bullets, bearing in mind rebates often start maxing out at 20mm or so. It may well end up that you entirely cannot stop assassins targeting you from outside but you can stop them so easily burgling you by using a gun to weaken the window. Then with whatever you save by not going mad on ballistic glass you can spend on a gun to actually have a semblance of reaction force if the risk ever crystallises.
• For example:
  • by comparing rated materials, we can deduce that 20mm poly glass would likely give you ER2 S blast and BR1 S ballistic,
  • we can easily get ER4 blast from the right layup of 24mm poly glass (Sicurtec Blast ER4 NS),
  • we can get BR4 from 23mm poly glass (Sicurtec Bullet) or 21mm ionomer glass,
  • we can get dual threat SR3 and BR2 from 20mm poly glass (Tecdur or ESG Secure) and SG1 NS, BR4 NS & P8B from 21mm poly glass (Polygard Pro),
  • alternatively 23mm polycarbonate (Hammerglass) is at least EXR2 (12mm is EXR2), plus BR4 NS and P8B (almost three times the thickness of Hammerglass 8mm P8B) – so majors on the biggest risk: manual attack, and is triple threat.
• Of the poly glasses, the Polygard Pro would be the winner if you feared guns more as it can handle one and maybe even multiple shotgun blasts, but with manual attack being the main worry the P8B rating leaves us wondering if it would also get SR3. For the same 23mm thickness polycarbonate handles all three threats, so unless a laminated glass manufacturer is prepared to add the missing blast or LPS1175 or LPS1270 rating or you would rely on your own calculations. If you feared sustained shotgun attack you would need 31mm poly glass.
• Beware you cannot assume thicker ballistic glass offers more than anti bandit protection against manual attack, eg the thicker Silatech ShooteQ BR4 NS 25mm poly glass is only P6B (although their SG1 NS 25mm is P8B). Also BR4 glass does not always also cover SG1, and BR6 may be needed before you can assume SG2.