Toughened Laminated – Higher Principles

Nigel Hearnden, Business Development Manager of ESG Group, examines the case for a return to the use of glass panels in balconies and balustrades above 18 metres from ground level.

Following the tragic loss of life at Grenfell Tower in 2017, no-one could argue that there was a prime duty of care towards those who work, and particularly live, in high rise buildings. However, a review of the Building Regulations in 2018, brought about a complete ban on the use of toughened laminated glass in balconies above 18 metres from ground level.

Was this the right call? We think not.

The use of glass above 18 metres above ground level is still permitted in windows and door panels – so why not in balconies? Essentially the reason that it was banned was that, despite the interlayer being fully encapsulated between panels of toughened glass, its presence makes up more than 1% of the total composition of a pane of toughened laminated glass.

As a finished product, toughened laminated glass does not combust or smoke in fire test conditions. We know this because we have subjected our latest product, ESG Pyrotech BSafe, to extensive independent testing. Made from fire-resistant glass panes laminated together, we developed this product specifically for use in high rise balconies. We then put the product through the strict testing process. The results were interesting.

Products for use in construction must be tested under laboratory conditions against EN 13501, which assesses whether a product will smoke, burn or drip. The first part of this testing procedure is called EN13823, which tests the finished product in fire conditions. As a finished product, the new fire-resistant toughened laminated finished product achieved a rating of A2, s1, d0, sufficient to make it suitable for use above 18 metres. However, as the interlayer makes up more than 1% of the finished product, it had to be tested further, in accordance with EN ISO 1716, which comprises a calculation of the gross heat of combustion of the interlayer alone. Under this calculation, the toughened laminated product rating dropped to a B.

We then tested our new product in accordance with EN 11925-2, which is an ignitability test, in which the finished product is subjected to a flame applied directly to its surface. The product is turned to allow the flame to make contact with more than one plane or surface of the finished product. Our fire-resistant toughened laminated product emerged completely unscathed.

What we have therefore, is an officially B rated product which behaves like an A rated product in live fire test conditions. It’s a dilemma for us as glass manufacturers, but we believe it could be easily solved by making this an acceptable compromise product for use above 18 metres. Arguably, it should also be an exempt product, as many other construction materials have already been designated.

Glass, clearly, is not a flammable material. Following the major London Underground fire of 1987, an extensive review of construction materials was also conducted. Glass was not banned for future use in the network as it was recognised that it was not a contributory factor to the spread of fire.

Other more recent, high profile fires in high rise properties have demonstrated that glass does not contribute to the spread of fire. In multiple examples, where fires have started in a single apartment, the neighbouring glazed balconies have remained intact; damage has not been extended to close neighbours.

The ban on glass has also had some unintentional fire risk consequences. Without the wind screening properties of the glazed panel, occupants have frequently turned to adding their own screening, most of which is highly flammable, and this cannot be effectively policed.

Since we submitted our opinion and evidence in 2020, there has, regrettably, been no further Government consultation with the glass manufacturing industry. This means that any advances in fire-resistant product development have not been acknowledged.

We now have a product which meets the desired aim of reducing fire risk, but is still disqualified because of a calculated test. It is high time the government took heed of this progress and made the enhanced fire-resistant toughened laminated glass an exempt product, allowing greater expression for architects once again, and an arguably safer, more pleasant environment for occupants.

In the meantime, we hope more discretion will be used by Building Control to recognise this as a compromise product, ready for safe specification above the 18 metre mark. It’s time to bring glass back to balconies.

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