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Spary foam insulation: benefits and disadvantages

Thinking about spray foam insulation? Read our blog post first!

In a period of rising energy costs, there has been a renewed focus on improving the energy efficiency of our homes. One product that is marketed for this is spray foam insulation.

When altering our homes, it is vital to obtain independent professional advice rather than relying on advice from contractors who may have a vested interest in selling a product. Installation of inappropriate products or poor workmanship can have devastating effects, especially in older properties.

The presence of spray foam insulation can cause difficulties should you want to remortgage or sell a property, as surveyors are likely to advise mortgage lenders that it is present and this can lead some lenders to refuse mortgages.

What is spray foam insulation?

It is a foam which is sprayed into position and sets. It is installed in lofts, in wall cavities, and under floorboards. It makes a property less draughty and provides thermal insulation.

There are two types of spray foam insulation.

Closed cell insulation is rigid foam. It is stiff and firm when touched. It forms a solid barrier which stops air and moisture.

Open cell insulation is a softer more flexible foam. It is squidgy when touched. It is slightly breathable so some air and moisture will pass through it.

What are the benefits?

Spray foam insulation can help to reduce heating bills as it is an insulator. It can also block some roof leaks.

What are the disadvantages?

Spray foam insulation is very hard to remove. If you want to re-roof a typical house, the slates or tiles cannot usually be reused and some or all of the roof timbers may also need to be replaced. This makes the job far more expensive. Similarly, with floor level spray foam insulation,  replacement of floors can require whole replacement of the floor joists.

The foam can trap dampness next to the timbers which causes structural timbers to rot. This can have catastrophic consequences, especially in older buildings.

When a spray foam installation is carried out, the foam often releases harmful fumes as it sets. Exposure to this can cause ongoing health problems for some people.

Spray foam insulation must never be used in Listed buildings or under thatched roofs.

If you find spray foam insulation in the loft, a surveyor will normally assume that the roof coverings are in fairly poor condition and that there will probably be some timber rot to roof structures which cannot be accessed or seen. Therefore, the presence of sprayed foam can cause difficulty in obtaining a mortgage and selling the house as it does tend to be looked at as a negative rather than as a positive benefit.

Your surveyor, when carrying out an L3 building survey inspection, should make the best endeavours to access and inspect all roof voids and loft areas in the property you are buying. If, however, the loft or roof voids remain inaccessible or are not accessed for whatever reason, the presence of any spray foam insulation in the building cannot of course be verified.

Author: Richard Ballam, Regional Director