'Spray foam insulation ruined our house sale'

Robbie, 38, had spray foam fitted in 2021 with the entire £5,733 cost covered by the Green Homes Grant scheme because he was eligible for certain benefits at the time.

He and his wife hoped to move to a bigger house in Nottingham, closer to potential secondary schools for their young daughter.

When they put their house on the market this summer, they quickly received an offer at asking price. But Robbie said he was "shocked" when the buyers' lenders rejected the property and they pulled out of the purchase.

Spray foam insulation has been used to stop heat escaping from roofs, lofts and attics for decades and comes in two forms.

Closed cell spray foam is rigid once set. It is a better thermal insulator and was previously sold to stabilise failing roofs. But if it has been used inappropriately or installed poorly, it might put stress on timbers, restrict air circulation and put them at risk of decaying.

Open cell spray foam remains soft once set and is only used for insulation. It is more breathable but is often installed where a highly-resistant underlay like bitumen felt is already present, stopping vapour from escaping.

Geoff Hunt, an independent chartered building surveyor, said open cell spray foam had gained popularity in recent years, bolstered by government initiatives.

But he said mortgage lenders struggle to assess spray foam, leading to "caution and refusals on higher-risk applications", for example, where it has been applied directly onto roof tiles.

Properly-installed open cell foam on a sound roof has not been conclusively linked to roof decay, he added, emphasising that it is important for homeowners with this type of insulation not to panic.

For homes where spray foam insulation is already present, the Homeowners' Alliance recommends:

Currently, it does not recommend installing spray foam until issues with lenders and rogue traders are resolved.