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Significantly increased fire risk in rainscreen cladding systems
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Significantly increased fire risk in rainscreen cladding systems
Professor Guillermo Rein, a professor of fire science at Imperial College London, presented the work of his team, which was based on an analysis of 252 fire tests carried out in a government-backed research facility in Poland, to the Tall Building Fire Safety Conference in east London. Get more news about terracotta cladding price,you can vist our website!
The work represents one of the first times a large volume of facade fire tests has been analysed scientifically, and therefore presents crucial insight into the risk which has become a major policy focus since the devastating Grenfell Tower fire in 2017.
Professor Rein explained that analysis of the data revealed a substantially increased risk for ‘rainscreen’ systems, which leave a gap, or cavity, between the external cladding panel and the wall of the building.
These systems performed consistently worse than rendered systems, where the insulation is applied directly to the wall without a gap, or sandwich panels, where the insulation is held within two sheets and comprises the structure of the wall. The research was based on data shared by ITB in Poland – a not-for-profit research institute under the control of Poland’s Ministry of Growth – which had included a footnote in the testing contracts to allow the data to be shared for scientific research purposes, providing the manufacturers of the products were not named.
The Polish test used a 2.8-metre tall mock facade, with a fan to introduce wind. Facades must pass three times in order to be classified as a success.
This differs from the standard UK test, which utilises a 9-metre mock wall, but has no wind and only requires one test pass for successful categorisation.
Professor Rein described the Polish test method as “absolutely wonderful”.
Analysis of the data showed that all of the rendered systems and sandwich panels tested had passed, but there were a significant number of failures among rainscreen systems – where 45% of the systems had some degree of failure and 11% failed seriously.
“Obviously it doesn’t mean that [rendered] systems and sandwich panels are always safe, but it does mean there is something going on in the rainscreen,” Professor Rein told delegates.
“The presence of a cavity augments tremendously the flammability of a facade. It does not mean if you don’t have a cavity you are safe, but if you have a cavity the level of worry should be multiplied by hundreds.”
Breaking down the failures by material type, all the rainscreen systems featuring terracotta, wood polymer composites and non-combustible aluminium composite material (ACM) had passed.
One failure was recorded in a cementious board cladding system, which combined it with phenolic foam insulation.
But a much higher degree of failure was found in ACM cladding mixed with fire retardants and even more so among high-pressure laminate (HPL) systems – where 11 of 15 tests failed.
The laboratory had not tested any polyethylene-cored ACM, the highly combustible material used on Grenfell Tower.
Professor Rein told Inside Housing that the laboratory had not tested any of these panels, due to a fear that their high combustibility would damage their facilities.