Fire-protective glass: An overview
Fire safety is, understandably, a primary concern for designers of today’s built environment, and glazing can play a vital role in achieving this. In this article we discuss the fire-protective glass on the market today, how to specify it in buildings and the regulations governing it.
Glass has become one of the most popular materials in the modern built environment thanks to its ability to provide a barrier to the elements and unwanted sound while still allowing light to flood into interior spaces.
Fire safety has also progressed rapidly in recent years. Since 1981, fatalities as a result of building fires have declined by around 20 per year, from 967 in 1981 to 265 in 2015. Much of this is thanks to innovations in technology, increased awareness of the risks and regulations governing building design. The glazing industry has responded to the fire-safety challenge by increasing its investment in research and development for fire-resistant glass as well as offering a wider choice of products with additional benefits.
Understanding the regulations
The Building Regulations, specifically guidance in Approved Document B (ADB), outline the basic fire resistance levels called for in glass positioned in different areas within a building.
The purpose of these requirements is to ensure that fire is contained within the room or space of origin and that the spread of smoke and fire is limited by fire-resisting compartmentation. This will ensure that the structural integrity of the building is maintained for a reasonable period, while also providing occupants and the emergency services with enough time to evacuate safely.
A key part of the regulations is that that the partitions separating areas within a building must achieve specific periods of fire resistance, which means the fire resistance performance of any glazing used in such walls is vital.
An aesthetic focus
Placing a focus on safety doesn’t mean designers have to cut corners when it comes to aesthetics or energy efficiency. Modern fire-resistant glass is incredibly versatile and has largely removed the need for compromise in these areas.
Historically, wired glass was predominantly used as fire-resistant glazing due to its ability to meet fire safety requirements. Although the glass still represents good value, it can limit the scope for designers and architects.
Nowadays, fire resistant glass is mostly completely transparent. This means a floor-to-ceiling glass screen can effectively serve the same purpose as a brick wall, something which has had a significant impact on building aesthetics.
This is made possible by making use of intumescent interlayers, which provide increased integrity and insulation. When heated, the intumescent layers turn opaque and expand to form a barrier to hot gases and flames, as well as insulating from the heat of the fire. It is possible for fire-resistant glass to provide complete protection against heat transfer for up to three hours, depending on its specification and system design.
A good example of this is Pilkington Pyrostop®, a multi-layer laminated glass comprising intumescent interlayers sandwiched in between glass layers, which is highly resistant to flames and the passage of heat as soon as it is exposed to fire.
A clear view
In certain situations, glazing systems that remain transparent while maintaining integrity when exposed to fire can be beneficial, particularly where insulation from heat is not as much of a concern, for instance, where a quick controlled evacuation can take place. These may also benefit the emergency services as they have a better view of the inside of the building, without having to expose themselves to potential danger.
Such products not only provide robust protection against smoke and flames, but also satisfy the aesthetic and performance demands of designers and architects. An example is the Pilkington Pyroclear® Line range of products, a 30-minute and a 60-minute integrity-only glazing system.
The system uses advanced toughened glass and offers floor-to-ceiling fire resistance with integrity performance using monolithic panes of standard soda-lime-silica glass, making it the first solution of its kind to be used without the need for obstructive framing.
Pilkington Pyroclear® Plus insulating double-glazed units, on the other hand, offer not only fire-resistance but also thermal insulation properties to reduce heat loss from a building. This can reduce heat-radiation for 60 minutes and in some configurations a 15-minute insulation value can be achieved.
With a continuous focus on innovation and new products entering the market, modern fire-resistant glazing systems will continue to be in high demand over the coming years. This, in turn, will bring increased responsibility for those in the glass industry to carry on investing in research and development and deliver fit-for-purpose systems as fire-resistant glass becomes more prominent in the built environment. The end result is buildings that benefit more from natural light, are energy-efficient and deliver high levels of fire protection.
Case study: 1 Aylesbury Street
Daylight-flooded spaces command a premium from tenants, but in the densest urban areas – where buildings are very tightly packed – it can be difficult to achieve. Not least because of the need to protect against the spread of fire.
This was the challenge for developer Meritcape when it set out to refurbish 1 Aylesbury Street – a converted historic warehouse building in Clerkenwell, East London.
The designers wanted to fill every floor of the building with natural light, from both the front and the back of the building, by using floor-to-ceiling glazing on every floor. However, the rear of the property was just three metres away from a neighbouring building.
To prevent fire spreading from one building to the next, building regulations specify the fire resistance that external walls need to be able to provide. This is given as minimum requirements for integrity – how long they can contain smoke and flames – and insulation, or how long they can prevent the escape of heat.
When two buildings are this close together, standard glazing is not an option, as it doesn’t put up enough of a barrier to fire spreading outwards from the property.
That’s where fire-resistant glazing can make a big difference. By providing protection against fire while also letting light flow in, we can create light-filled spaces in very built-up parts of the city where not long ago it wouldn’t have been possible.
As well as sealing in flames and smoke for at least an hour, the glass also provides radiation shielding that reduces the amount of heat energy that can pass outwards through the glass – another key means of spreading fire.
The rear façade of the building is glazed in Pilkington Pyroclear® Plus insulating double-glazed units, delivering not only the right level of fire resistance, but also, with unit design, offering excellent thermal insulation (U-value) properties to reduce heat-loss from the building.
Those looking for modern commercial space expect floorplans to be well lit with natural light, and this is one of the main design challenges when working with buildings in urban areas.
Pilkington fire-resistant glazing means the best of both worlds can be achieved – a building that meets or exceeds all of the safety regulations while also feeling spacious and airy.
A total of 800m2 of Pilkington glass was used in the project, including in the front façade of the building, in which hundreds of custom-sized small double-glazed low-e units were used to imitate the Crittall steel-framed windows that are a signature feature of buildings in the area.
For more information, go to www.pilkington.co.uk/fire