UK Spray Foam Insulation: Key Facts & Statistics

Journalists, researchers and publishers are welcome to reference this page with credit to the National Spray Foam Advisory. Figures were correct at the time of writing; lender positions in particular change over time.

How many UK homes have spray foam insulation?

To put that in perspective, that is roughly the housing stock of a city the size of Nottingham. Much of it was installed in good faith — often marketed on energy savings — by homeowners who had no reason to expect it would later complicate a sale or a mortgage application.

How often does spray foam cause problems?

Two things are worth saying about that number. First, it is a serious figure — roughly one home in three, from a meaningful sample. Second, it is a minority: most inspected homes did not have a defect resulting from the installation. Both halves matter. The honest reading is not “spray foam ruins every roof” and not “there’s nothing to worry about” — it is that every home, and every installation, is different, which is exactly why an individual assessment matters more than a headline.

What do mortgage lenders say?

Positions differ between lenders and change over time — which is why we deliberately don’t publish a named-lender league table on this page. The practical question for most homeowners is not which lender, but whether the roof’s condition can be shown to be sound. Our mortgage problems guide and lenders guide cover what to do about it.

Why do lenders hesitate? The mechanism in one paragraph

Spray foam converts a ventilated “cold roof” into a warm roof, and closed-cell foam also acts as a vapour barrier. RICS notes that moisture below the roof covering “might not escape or dry out properly” and water vapour in the roof void is “less likely to be vented away” (RICS Built Environment Journal). Just as importantly: a surveyor cannot see or test the timbers the foam covers, so a lender’s valuer often cannot confirm the roof is sound. Lenders decline because the risk is unverifiable — not because damage has been proven in that home.

Is the damage proven?

Treated carefully by RICS itself: damp conditions around timber are a recognised risk, but the evidence on widespread timber decay is limited — RICS notes that if decay were a major problem with spray foam, more confirming research would be expected. Battens and timber decay are “often cited” rather than established. This is why responsible advice says can and may, not will.

Open-cell vs closed-cell

Open-cell foam stays relatively soft and allows some vapour movement — a lower condensation risk. Closed-cell foam sets rigid and blocks vapour — a higher risk where it was installed without ventilation provision (RICS / industry). Which type is in a loft, and how it was applied, changes the picture substantially — RICS also notes that gaps in poorly applied insulation “could then permit air leakage and consequent condensation on the underside of the roof covering.” (New to the jargon? See our plain-English glossary.)

What is the government’s position?

Removal is not automatically the answer — and any adviser who tells you otherwise before examining your roof is ahead of the evidence.

What do the professional bodies advise?

Both RICS and the Property Care Association recommend an independent professional assessment before making decisions (CBP-10658). The HomeOwners Alliance goes further on new installations, advising homeowners to avoid installing spray foam roof insulation until the industry’s issues are resolved. And for older or historic buildings, RICS describes spray foam on a heritage property as “an extremely unwise course of action.” If a survey has already flagged foam in your home, our survey guide explains the sensible order of events; typical removal costs are covered in our cost guide.

Sources: House of Commons Library briefing CBP-10658 · HomeOwners Alliance · RICS Built Environment Journal · Property Care Association & HomeOwners Alliance joint letter (May 2025) · BBC research (November 2024).