Grenfell Inquiry day 78: insulation and cladding materials ‘below required standards’

Dr Lane said she had seen no evidence from a test which could allow the insulation to comply.

She said that insulation products used within the window construction was Class F and Class E respectively – five and four grades below A2.

Dr Lane said that while Approved Document B was not clear on the standard required for windows, she believed it should be required to be limited combustibility.

The cladding meanwhile, aluminium panels with a polyethylene core manufactured by Arconic and branded Reynobond 55PE, was a European Class E, she said.

Significantly, she said the cladding was required to be a lower standard than the insulation by building guidance – Class 0 or Class B rather than limited combustibility or Class A2.

This is an interpretation which is common in the industry but government sources have vigorously resisted since the fire.

Reynobond PE was given a British Board of Agrément (BBA) certificate rating it as Class 0 or Class B, leading some to believe it would comply with this requirement, but Dr Lane has said this certificate itself was “factually incorrect”.

Among other things, she explained to the inquiry today that this was because a cassette system (as used on Grenfell) had not been tested to support the findings of the certificate.

She said: “At Grenfell Tower specifically we have a cassette system, and I have seen no test evidence where a cassette system performs to the requirement of Approved Document B.”

Dr Lane was also asked whether ‘mineral wool’ insulation products – widely seen as a non-combustible alternative to plastic foam insulation – could be considered combustible, a question she responded to firmly.

She said: “Do I have to answer that question? Mineral wool is non-combustible, the binders used to pack it together are combustible. But I find those arguments quite trite when one compares mineral wool with a polymeric foam of equal thickness. I understand that nearly everything in the world can burn but in the context of construction, I like to keep things appropriate and relevant and understand that a mineral wool is substantially less combustible and typically defined as non-combustible.”

She also rejected the use of post-Grenfell BS 8414 tests, commissioned by the government, to compare the performance of mineral wool and plastic insulation. She said: “I don’t take anything from those tests because I don’t consider them to be relevant because they are so far away from the kind of construction detailing that people like me have to deal with in our profession.”

Dr Lane promised a “detailed chapter” on this issue in a further report for phase two of the inquiry, should it be required.

The inquiry continues.