Recent developments in glass processing mean that fire resistant glass can now also be used for additional reasons such as security and sound attenuation. Scott Sinden, managing director of UK glass processor ESG explains how glass has become more versatile.

There are two main types of modern fire resistant safety glass: integrity only, or integrity and full insulation. Integrity only fire resistant safety glass (denoted as type ‘E’ under BS476 Pt22 and BS EN 1364 Pt 1 1999) is designed to contain flames, smoke and hot gases in the event of a fire. For many commercial applications, this will be an ideal cost effective solution.

Integrity and full insulation fire resistant safety glass (denoted as type ‘EI’ under the same standards) can not only contain flames, smoke and hot gases – as with integrity only glass – but also delays the transfer of radiated heat. Where highly flammable, potentially explosive or toxic materials are stored, this type of glass may be specified in specific rules of storage, and is a wise precaution.

However, we can now do far more with fire resistant safety glass than we once thought possible. New, highly technical glass products can provide added personal safety, enhanced security, sound attenuation, privacy, and even a combination of all these things. This has given the specifier far more scope to solve several problems at once, without compromising on the fire resisting properties expected by the fire safety engineer.

Safety in technology
To the inexperienced eye, one pane of glass may still look much like another, but with recent advances, this couldn’t be further from the truth. Demand from architects to use glass in both decorative and practical ways has helped spawn a new generation of safety glass, the properties of which glass processors have since also incorporated into fire resistant safety glass.

One of the main problems with glass is how it behaves when damaged – something that increases in probability in the event of a fire. A protective shell against the elements when intact, when broken, glass becomes an active potential hazard, creating sharp shards which pose a serious risk to life and limb. The obvious answer might be to use toughened glass with built-in fire resistance, but even this is problematic. Although toughened glass shatters into far smaller and less individually dangerous pieces, the use of glass for roofs and in large panels at high level still means that if it gets broken, it can produce a large shower of glass fragments, which can still inflict considerable harm when falling from some height.

The answer has been the invention of toughened laminated glass. Lamination was actually discovered by chance just over a century ago by French scientist, Edouard Benedictus, but it has only been in the last few years that the glass processor has devised a way to combine toughened, laminated and fire resistant properties into a single safety glass product.

Most toughened laminated glass is available in a wide range of interlayers and thicknesses and can be used to satisfy safety glazing requirements, as specified in part N of the Building Regulations and BS 6262 part 4. Subject to calculation, it can be used to form full height barriers in compliance with approved Document K of the Building Regulations, as well as with BS 6180. A typical toughened laminated glass panel will comprise two sheets of toughened glass, in a choice of thicknesses, and a tough, clear interlayer of either PVB (PolyVinyl Butyrall) or EVA (Ethylene and Vinyl Acetate copolymer). These are bonded together under heat and pressure and, once sealed, they become a single unit. Because toughened glass is highly resistant to impact, it is an ideal material to use in areas of high pedestrian traffic, such as shopping centres, hotels, sports facilities and corporate offices.

Using panels of fire resistant toughened glass laminated together can now offer a highly effective barrier against fire. In the past, this wasn’t possible, as larger panels of fire resistant safety glass which could be used in large steel frames just weren’t available. Recent advances in glass processing now mean that panels of up to 4.9m2 can be produced to exact specifications and can be used with large steel screens – provided that the combination of glass and frame has been tested and approved by an accredited independent body. One such testing facility is Exova Warrington, which has recently approved fire resistant safety glass for use in steel frames to provide either 30 or 60 minutes’ resistance, according to specification.

The fight against crime
Secured by Design is an initiative to encourage the reduction of crime against property by designing it out of the built environment. Perceiving this demand for more secure products, glass processors set about developing products that would address the need for greater security, while still providing the required degree of fire resistance. The result has been a range of new products which are approved by the Secured by Design initiative for providing high levels of resistance to manual attack.

Fire resistant glass can also give protection against manual attack

Recent developments in the use of lamination and technically advanced interlayers have meant that glass processors can now produce an exceptionally sturdy glass which gives protection against damage or intrusion, as well as providing fire resistance to 30 or 60 minutes, depending on the building’s requirement.

Quietly confident
A growing need in new build construction is sound attenuation. Once something that was viewed simply as a nuisance, the passage of sound is now governed by part E of the Building Regulations, and most architects will now stipulate a level of sound attenuation which must be achieved in the construction of the project.

By using specially formulated acoustic interlayers with relatively thin layers of toughened fire resistant safety glass, the processor has been able to develop a product which gives good resistance to sound, but which is significantly lighter and easier to handle for the installer. This still gives good protection in the event of a fire and will, if damaged, hold all the resulting pieces in place.

Behind closed doors
Fire glass itself can now also be used to provide privacy where needed. A new breed of interlayer – known as privacy film – has been developed. Sheets of fire resistant safety glass can be laminated together using the privacy interlayer to form instant screening which changes from diffused white to optically clear at the flick of a switch. The interlayer contains randomly oriented fibre strands which provide an opaque appearance and afford privacy to the occupants of a room or cubicle. This makes it ideal for boardrooms and even for shops, as this provides a surface

A special film can provide privacy at the flick of a switch

onto which presentations or advertising messages can be projected, obviating the need for a separate screen. With the switch set to off, no electricity passes through the interlayer, and it remains in its white state. Flick the switch, however, and a small electrical current passes through the film, causing the strands to line up and the glass to become optically clear and see-through.

Each project will have its own requirements, and it’s now even more important to discuss the glazing with the glass processor well in advance, as they may well have a better view on what is or isn’t possible. Choosing a member of the Glass and Glazing Federation’s Fire Resistant Glazing Group makes good sense, as does consulting its guide to best practice, which is available here. Similarly, if security is a prime consideration, a sensible first port of call is ACPO’s Secured by Design website.

Interlayer technology has now lifted glass production to new levels of versatility and opened up real possibilities of addressing several practical problems in a single product. The interlayer process allows us to combine fire resistance with sound attenuation, safety of the individual, security of the building and privacy in a single glass product. Glass can now be seen as a highly technical product with more to offer than ‘Break in Case of Fire’.

Scott Sinden is managing director of glass processor ESG