ÐÇ¿Õ´«Ã½

The Glass & Glazing Federation’s Guide to Best Practice in the Specification and Use of Fire-Resistant Glazed Systems was hailed as a landmark publication at its launch event at RIBA on 1 September. It has been developed by the Fire Resistant Glazing Group (FRGG) to help all those who specify, design, supply, install and depend on fire-resistant glazed systems.

The Guide is available in hard copy and as a free download from the GGF website, which should ensure that the document is widely circulated and referred to.

Mike Wood of Pilkington, FRGG Chairman, began the launch event by giving an introduction to the definitive best practice guide. The programme continued with contributions from Anthony Burd from the Office of the Deputy Prime Minister, Nick Pamphilon of Ian Ritchie Architects, Steve Cooper, Director of Warrington Fire Research, and Kevin Towler of Chiltern Fire.

Whilst welcoming the recently published Guide to Best Practice by the GGF, the comments of some of the experts chosen to launch the guide – from the fields of practising architects and professional fire engineering consultants – threw light on some areas of heated debate between the different product makers who serve on the GGF Fire Resistant Glazing Group (FRGG) committee.

Question time revealed a lack of consensus on the levels of insulation from fire that might be required, especially with regard to adjacent buildings – an area still exposed to the vagaries of building control.

Radiated heat threat

Fire glass specialist CGI International was one of the 19 FRGG members that assisted with the Guide. Says Managing Director Tom Ritchie:

It is ironic that part of the subject areas chosen by the two independent ‘launch’ speakers – one from a leading architectural practice and one from a professional fire consultancy – should both focus on the threat of fire spreading due to radiated heat levels – an area almost ignored in detail by the Guide to Best Practice.

Due to the wish for the FRGG to publish a consensus document, certain fire performance features not mandated by UK ÐÇ¿Õ´«Ã½ Regulations were downgraded by emphasis in the Guide – but that does not mean they do not exist!

The un-insulated fire glass types which remain clear during a fire will allow huge amounts of radiated heat to pass through them and cause a potential early ignition of anything flammable in their path – the new European Norm tests easily identify this potential by measuring and reporting radiated heat and by trying to ignite a cotton pad with the transmitted heat level (no flames) – guess what, clear glasses fail the cotton pad test at around 10 minutes!

Some of the more recently developed fire glass types, even though they are still classified in the UK as ‘INTEGRITY ONLY’ – without insulation, are laminated, with the interlayer(s) designed to react to a fire threat – clouding over to reduce the passage of (mainly) radiated heat. The actual performance differences between glasses with a reactive interlayer and those that stay clear – including polished wired types – is very considerable and in European markets, the reactive interlayer glasses properly have their own ‘slot’, controversially called partially insulating or radiation controlling. This differential status is somewhat downplayed by the Best Practice Guide due to the need for consensual commentary.

Ironically the radiation control data was precisely the area focused upon by both the independent fire experts in their papers on fire safety. They know that there is no point in providing an integrity fire barrier for up to two hours, when the radiated heat transfer levels will be enough to ignite spontaneously many common items of the building fabric – see the experience of the cotton pad test above – at less than 30 minutes.

In a positive role, they also know that if you can deal with the radiated heat issues, you can often solve the fire threat problem – these are some of the considerations they apply, when looking for a fire-engineered solution.

In some European countries, using the same European Norm (EN) test, a maximum level of radiated heat is prescribed but the idea that we can ignore this concern in the UK, just because it is not yet called for by ÐÇ¿Õ´«Ã½ Regulations, seems ludicrous, especially in the knowledge that fire experts, including those who launched the Best Practice Guide, already take the radiated heat issue into consideration.

CGI International Limited is a specialist UK-based fire glass manufacturer, offering a comprehensive range of fire glasses.