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Combustible insulation was chosen for the refurbishment of Grenfell Tower because it fitted with an “aspirational” energy efficiency target, an inquiry has heard.
The Celotex material inside the cladding around the west London block contributed to the spread of the fatal fire in 2017.
Andrew McQuatt, project engineer for consultancy Max Fordham, who was tasked with the Grenfell refurbishment, told Thursday’s hearing that the insulation was a “top priority” for those involved with the project.
Mr McQuatt, who worked on the tower between 2012 and 2013, suggested using Celotex on the tower, as renovators tried to hit a U-value target.
A non-combustible Rockwool was decided against because the team thought it would be too thick for the system they were planning, however, calculations done by the inquiry showed to Mr McQuatt suggested otherwise.
The U-value of an insulation material is set according to how heat escapes or travels along the building, with the aim of retaining heat in winter months, and cooling in the summer, the lower a material’s U-value, the better it is in terms of its thermal efficiency.
The desired U-value for the Grenfell Tower refurbishment was set at 0.15, more commonly seen on new-builds, whereas the regulation recommendation for projects of this type suggested a 0.30 target.
An email from architect Bruce Sounes in July 2012 to Mr McQuatt and other colleagues at Max Fordham described the 0.15 figure as “a bit aspirational”.
However, Mr McQuatt recalled repeatedly hearing from colleagues that they should be working towards new-build targets, and thought it fitted with the type of work being done at Grenfell.
He told the inquiry: “If you were to build a tower from scratch and you were to build a concrete tower, apply insulation to that concrete frame and apply rainscreen, that didn’t seem any different to doing the renovation.
“Because it was how similar to how you’d construct a new-build, those new-build targets didn’t seem crazy.”
He added: “I didn’t ever think of it as an overly ambitious target,” and said that on new-build projects across London: “It would be common to come across even lower U-value targets.”
Rather than be concerned about the target, Mr McQuatt said he felt “quite positive” that firms were willing to get behind it.
He explained: “Here was an aspirational target being proposed and there were people who were willing to go for it because they believed in it.”
The inquiry will continue next week.