The Amazing Fire Resistant Glazing!
In modern building design for commercial properties, where a structure may be hundreds of meters wide and hundreds of meters deep, entire building facades can be composed of glass in order to allow entry to the maximum possible amount of light. However, in order to compartmentalise and protect against the spread of fire, designs could result in the increase of barriers to light penetration and subsequently the lack of it reaching pasty pale office workers and creating gloomy, isolated working conditions.
The desire of architects has been to open up the design of office buildings and use more glass, such as lobby atriums and glass walls. Some modern glass behemoths, such as the 30 St Mary Axe (The London Gherkin building), are comprised heavily of glass and represent the cutting edge of architectural engineering.
First you see it, Now you don't
In these modern offices where there is an extensive use of glass internally, it is not uncommon for individual offices to be bordered by at least one glass feature and for the truly modern premises for two or three if not the entire office perimeter to be glass composed. This presents something of a potential problem for fire engineering.
Glass softens over the range from 500˚c to 1500˚c. A flame from a candle burns between 800˚c to 1200˚c. As an example, in a typical office post flashover fire temperatures reach between 1000˚c to 1400˚c(1). These temperatures will certainly be enough to disrupt the integrity of nearby glass panes. The main failure mode for conventional glass is the advent of cracking and collapse caused by thermal shock and temperature differentials across the exposed face. This will compromise the compartmentalisation of the building's interior allowing fire to spread more easily from room to room.
A solution to this would be to use fire resistant glass. It certainly exists, and in some cases has a long track record of success, but as to be expected it comes in many forms and with varying levels of performance.
Pulling Fire Protection out of the hat
There is a clear distinction in the types of protection fire resistant glass offers.
Protection is based on either integrity only or integrity with insulation.
Integrity defines the ability to hold back flames and hot gases. It is essentially a barrier to the spread of flames but does not stop heat.
Insulation is a much higher level of performance which limits heat transfer from the fire, both providing a barrier to the spread of flame and stopping heat by all heat transfer mechanisms through the glass.
The distinction between these two performance classes must not be blurred, as the differences in performance - and consequences in a fire - can be huge.
Integrity only may lead to high temperature conditions on the fired side and levels of radiant heat that cause both serious life-threatening burns
to people and secondary ignition of objects on the non fire side of the glazing.
Integrity and insulation provides the barrier to fire and excellent protection against heat giving crucial advantages for enhanced life safety, as well as benefits in limiting fire spread in condition of exposure which may be hours not minutes,
Pick a Supplier from the pack
With the different forms of protection available it is important to choose a manufacturer's product type that is relevant to its intended end use requirements. Conversing with a suitable supplier early on as to what products are available and what levels of protection they offer is certainly a good idea. Product price may also be a factor in deciding the fire safety plan with the project certainly having been set budgets on fire safety expenditure. But the required performance specification has to be sacrosanct because of the dangerous unpredictability of fire.
An obvious first choice of supplier would be world renowned manufacturer and everyday household name for Glass, Pilkington. With a pedigree in glass dating back to 1826 Pilkington have constantly been at the cutting edge of development and product innovation in the field. As function of this they added and continue to develop fire resistant glazing as an integral part of their product range. All fire resisting products are compliant with the relevant BS and European standards, ensuring quality every time.
Products include
Pyrostop - Up to 180 minutes Integrity and Insulation product
Pyrodur - Up to 60 minutes Integrity (and some measure of insulation, for 15 minutes)
Pyrodur Plus - Up to 30 minutes Integrity and (and some measure of insulation, for 15 minutes)
Pyroshield - Up to 120 minutes Integrity
only product (in the right framing system)
As part of their commitment to customer service Pilkington offer the on-line product consultation system called 'Specfire'. By answering a series of questions you are taken to a screen highlighting the relevant product, its properties and performance, including fire test summaries.
The Grand Finale
One of the most important considerations of its use is not only the correct choice of product but also ensuring correct installation procedures are followed.
The Glass and Glazing Federation produce a best practice guide, produced by the Fire resistant Glazing Group under the chairmanship of Pilkington's Mike Wood, which sets out the best practice for the installation, specification and use.
With the trend of using more glass in a structure, fire safety will certainly need additional consideration and as early in the design process as possible to take into account budgetary constraints and the limits of fire resistant glazing. The upcoming BS 9999 contains revised guidance on the subject as a result of a better understanding of how glass behaves in conflagration conditions due to testing over the last five years(2).
Although a valuable tool fire resistant glazing is to be considered as yet another weapon in a fire engineer's arsenal of protective measures requiring careful deliberation as to application and integration into the overall fire safety strategy.
For further information visit www.pilkington.co.uk/fireresistant or contact the Pilkington Technical Helpline by email to Pilkington@respond.uk.com or by phoning 01744 692000.
Footnotes
(1) www.wikipedia.org/
(2) FSE June/August P.29
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