Why is it hard to sell a house with spray foam insulation?

It is harder to sell a house with spray foam insulation, particularly closed-cell spray foam in the attic roof deck, because of lender, inspector, and buyer concerns, even though spray foam itself is a high-performance product. The biggest issue is in the UK and increasingly in the US, mortgage lenders and home inspectors are wary of spray foam applied directly to roof sheathing. Lenders worry that spray foam can hide roof leaks, trap moisture against wood, and make it impossible to inspect the roof deck for rot or damage without removing the foam, which is expensive. In the UK, several major lenders have declined mortgages on homes with spray foam on roof rafters. In the US, home inspectors often flag spray foam in attics because if the foam was installed incorrectly or without proper ventilation, it can cause moisture problems and void shingle warranties by making the roof deck hotter. Open-cell spray foam is less controversial than closed-cell because it is vapor permeable. Another reason is cost of removal. If a buyer wants to re-roof or rewire, removing spray foam costs $3 to $6 per square foot. Poorly installed spray foam can also off-gas odors if not mixed correctly, leading to indoor air quality complaints that scare buyers. To make a sale easier, provide documentation of professional installation, brand used, and proof that roof ventilation was addressed.