The Centre for Sustainable Energy (CSE) reviewed its spray foam insulation advice in November 2025, stating that in almost all cases installing it carries considerable risks and that other forms of insulation, such as standard mineral wool rolls, should be considered first1. Spray foam is made of polyurethane, sprayed wet onto surfaces where it sets into a solid foam, and is most often used in lofts on the underside of sloping roofs, or under suspended floors1.
The review sets out several concerns. A study by the Health and Safety Executive suggests spray foam insulation causes timber decay in more than a quarter of all cases1. Because the foam coats the underside of a roof, it hides the rafters and roof lining, making leaks and repairs difficult to spot, and a layer of foam makes a survey of the roof impossible, which may mean solar panels cannot be installed1. CSE also states that removal is very difficult and can be very expensive, in the £1,000s for most properties, and that the presence of spray foam can make homes harder to sell, particularly if a survey finds it was poorly installed1.
"CSE’s view is that in almost all cases installing spray foam insulation carries considerable risks.
Two types are described. Closed-cell foam is not vapour permeable, which makes it a better insulator but means moisture cannot move through it, and CSE says it is more likely to cause damp problems than open-cell foam1. Open-cell foam is more vapour permeable, more flexible and better for sound insulation, but more fragile and less effective as an insulator, so a thicker layer is needed1. CSE also notes that harmful fumes are produced during installation and in the days the material takes to set, that spray foam is much more expensive to install than mineral wool laid on a loft floor, and that listed building consent is required before installing it anywhere in a listed property1.
| Type | Vapour permeability | Insulation performance | Notes |
|---|---|---|---|
| Closed-cell | Not vapour permeable | Better insulator | More likely to cause trapped moisture1 |
| Open-cell | More vapour permeable | Less effective, thicker layer needed | More flexible, better for sound, more fragile1 |
CSE adds that rogue traders are known to use aggressive sales tactics to pressurise homeowners, sometimes telling them their existing insulation is illegal or dangerous, and that some mis-sold homeowners are later targeted again with claims the foam must be removed urgently1. It says such decisions are never really that urgent1.
Why it matters for households
Insulation is central to a home's energy independence, but the wrong material in the wrong place can work against it. Trapped moisture can rot roof timbers and floor joists, and the cost of putting that right sits with the householder. A foam layer that blocks a roof survey can also close off later options, including solar panels. Where spray foam has already been installed, CSE states that damp and mould warrant extra attention, and that removal is difficult, disruptive and expensive, with standard loft insulation possibly needed afterwards1. It has not been reported how many UK homes have spray foam installed.
What happens next
No further review date or regulatory change is given. CSE's guidance was reviewed in November 2025 and remains its current published position1.