Spray Foam "Banned" in the U.K.

While not officially banned, most insurance companies and mortgage lenders will refuse a house with spray foam insulation (read more). We have thought for years that spray foam as the Cadillac of insulation materials with budget most often being the reason for choosing another material. So why does the UK have an issue with? And why should we here in the US as well?

Spray foam is the result of a chemical reaction that occurs during installation. Chemicals are mixed from the installer’s truck and the ratio of them is controlled by the installer. If this mix ration is even a little off the resulting product will not perform as promised.

In order to perform well, the cured spray foam needs to stick to the wall or roof sheathing to which it is applied with no gaps. This is where the problems occur – improperly mixed foam will pull away from the sheathing. These gaps are no longer air tight. When moist air enters these gaps, condensation forms and has nowhere to dry. Condensation is water. Standing water and wood mean mold and rot. You see where this is going.

This photo shows a real life example of spray foam pulling away from the wood. We found this when pulling apart a house in preparation for an addition – luckily this area would be completely removed. The green arrow represents the one-way vapor flow. If this were against a roof deck or wall sheathing, outside air would get stuck in that gap and condensation would form since the water vapor in the air has nowhere to go.

Nobody wants hidden mold and a rotting house and this has become such an issue in the UK that lenders and insurers insist that all spray foam be removed and replaced with a “breathable” option like mineral wool. At House to Home Design & Remodel, we use mineral wool and blown-in cellulose as they offer drying potential. We also make every effort to seal against air leaks to minimize any potential for issues.