Spray Foam Insulation - A surveyors view

When it comes to selling homes, majority of buyers will have a survey on the property they are buying to ensure there are no major issues they will run into when they move in. I recently had a case where a property I was selling had installed installation foam into the attic space/roof causing an issue with the transaction. This caused lots of stress between both the sellers and buyers of the property and a large sum of money had to be paid out to get the whole situation rectified. Think twice about having this installed and read the article below from my good friend at ATR estates.


Spray Foam Insulation- A Surveyor’s View - A T Rowland BSc FRICS FNAEA


Spray Foam Insulation has been available for the past 30 years and has been advertised by the manufacturers not only to improve the insulation of the loft but also to repair old roofs suffering from failures such as nail fatigue and water penetration as the foam binds together the covering, the battens and rafters. Applied in liquid form, the material expands to the required thickness then sets in a rigid foam state, providing a continuous, seamless thermal barrier which is it is claimed eliminates draughts and condensation problems, saving energy and costs. 


There are two types.


 Open-cell foam – this type is very light, easy to tear and allows water vapour to pass through into its structure where it can form interstitial condensation and wet the insulation. It requires a vapour barrier so is not recommended in the UK.


 Closed-cell foam – this is much denser and more expensive than open-cell insulation and acts as a vapour barrier. It’s not easy to tear and it forms a much thicker and harder skin that provides higher levels of thermal efficiency.


 The problems with sprayed foam insulation. There does not appear to be much in the way of reliable scientific evidence. Most information is authored by suppliers, and for that reason may be less reliable. In practice, however, many mortgage companies refuse to lend where the foam has been installed making it hard for the homeowner to sell. Such attitudes will undoubtedly affect property values. 


Moisture levels. The main concerns are that despite the claims from the manufacturers, sprayed foam can cause condensation resulting in rot and decay to the roof structure. Surveyors argue that interstitial condensation could occur on the cold side of the insulation and cause decay in the tiling or slating battens or the rafters themselves, often not visible from an internal inspection. The quality of the application is crucial. The rafters should not, for example, be totally encased in the foam and if the insulation is efficient at forming an air barrier then it follows that any water vapour finding its way into the roof void needs to be ventilated to avoid condensation. Where foam is applied to the roof slopes a warm roof is created which means any insulation at ceiling height must be removed. Any moisture finding its way below the roof covering might not escape or dry out properly – particularly if closed-cell insulation is used – leading to raised moisture content and subsequent risk of decay to the roof timbers. Depending on the underlay type, a vapour-control layer may still be needed on the warm side of the insulation. Gaps in the insulation, if poorly applied, could then permit air leakage and consequent condensation on the underside of the roof covering.


 Removal. It is difficult and very labour intensive to remove and virtually impossible to reuse the existing materials. Unlike a conventional roof covering repair, the battens and rafters often have to be replaced as well. However, there are now companies that specialise in the removal of sprayed foam.


 It produces gasses. Because it is mixed on-site as opposed to rigid foam insulation, the chemicals used in the manufacture of foam are quite noxious and can cause problems as a result of off-gassing. This was a known problem with early formaldehyde, although the effects were usually transient and the gas dispersed after a few days. Older formaldehyde foams have been known to degenerate over time, sometimes breaking down or crumbling and in doing so releasing irritant dust that can be harmful to susceptible individuals. The crumbling and shrinkage of spray foam is often associated with problems in the mix proportions or formulation of spray, possibly due to inexpert application.


 PVC Cables. There have also been concerns over PVC insulated cables that come into contact with sprayed insulation. Modern formulations are less likely to cause problems, but the encasement of cables in insulation could lead to a need to de-rate them to a lower operating current. The foam products must not come into contact with zinc or zinc-plated elements, such as truss clips or gang-nail plates, because the foam will accelerate the corrosion of these under certain environmental conditions. Like many things, the results of poor application can bring a system into disrepute, and with many DIY spray foam kits now becoming available, one could rightly understand a cautious view of the results of an inexpert application.


 Cost. For the level of claimed benefits, the cost is very high, compared with conventional insulation giving the same heat-loss values.


 Environment. If applied directly to tiles or slates they cannot be reused as they would be normally with conventional re-roofing and those precious, recyclable materials will end up in a landfill site. This is not only bad for the environment but adds to the cost of eventual reroofing.


Wild claims and Listed buildings. One trade association's marketing material claims "spray foam applied to the underside of tiles prevents theft". Others claim the treatment is particularly suitable for use in Listed buildings, ignoring the fact that such work always requires Listed Building Consent, which will never be given due to the destruction of period materials.


 Guarantees Unfortunately, many of the guarantees issued by the installation companies only cover the potential decay to the foam itself and do not cover any damage caused to the building by the installation, so are meaningless. Checks should also be made as to whether the guarantee can be transferred to subsequent homeowners.


 In conclusion. Concerns over spray foam might not be fully supported by examination of the evidence, and failures could be due to a combination of other causes rather than the foam itself – for example, high humidity, poor ventilation or the presumption that a roof covering in poor condition can somehow be made sound by a sprayed coating. Even a conventionally insulated roof void could also suffer from acute condensation; a lack of ventilation coupled with high levels of insulation and poor vapour control can cause rot to the roof timbers so it would be wrong to criticise sprayed foam simply based on perceived risk. However many property professionals do not recommend this type of application and until mortgage companies change their attitude, my advice is to view the treatment at best with caution and at worst to avoid it, especially in listed buildings. At the very least, agents must make sure their clients are made aware of the pros and cons.


 Grants. The Green Homes Grant scheme launched in September 2020 which offered home insulation of up to £5,000 per household in England comes to an end on 31st March 2022. During this time and in previous years many thousands of lofts were insulated with sprayed foam insulation. Some energy companies offer free insulation or grants to help you make your home more energy-efficient, thanks to the government’s Energy Company Obligation (ECO) Scheme Further independent advice is available from Simple Energy Advice on 0800 444 202.


 © ATR Estates Ltd March 2022 

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