Energy assessors have long been concerned about the claims being made to sell spray foam insulation to unwary property owners. The idea of partially encapsulating structural timbers in foam, in whatever condition they happen to be, seems extremely high risk and counter to what we know about maintaining building integrity. 

From an energy efficiency point of view, it is hard to see how this can be the best way to insulate a roof in all but a very limited set of circumstances. To spray insulating foam on the rafters and pitched construction of a “cold roof” (one which is ventilated to the outside) is an exercise in futility. The heat has already been lost. Even in a “warm roof” scenario, unless your primary purpose is to stop draughts, spray foam would seldom seem the most logical approach. 

Unscrupulous sellers are claiming many unsubstantiated benefits for spray foam insulation. I have personally been called more than once by someone claiming to be my local energy efficiency advisor and telling me my house is at risk because I have the old fashioned type of loft insulation. He also claimed that I would be losing much less heat if I replaced it with spray foam. (You can imagine how that conversation went). 

The truth is that in virtually all cases, you will get a worse Energy Performance Certificate (EPC) rating from spray foam insulation than from the other more traditional (tried, tested and time proven) methods of insulation. The reason for the lower EPC rating is simply that it is not as good at insulating your roof as those other methods. Anyone who tells you that you should remove a decent layer of insulation at joists and replace it with foam insulation almost certainly does not have your best interests at heart. You are very unlikely to be told to do that by anyone who does not stand to make money out of you buying spray foam insulation. 

Given the above, it comes as no great surprise to find that property surveyors do not generally think it is a good idea either. 

A recent investigation by the Residential Property Surveyors Association (RPSA) concluded that surveyors should “adopt a highly cautious approach, recommending removal of the spray foam in almost every case”. 

Read the full press release at https://www.rpsa.org.uk/clientfiles_uploads/website/RPSA_Spray_foam_insulation_release_-_20.12.21.pdf  

If you are thinking of insulating (or adding additional insulation to) your roof, someone may well try and sell you spray foam insulation. Before you go for it, remember that it scores worse than most other types of insulation in an EPC, and that lower rating can reduce the value of your property. When you come to sell, your buyer’s surveyor is likely to recommend to your buyer that it should be removed which is probably going to reduce the amount your buyer is willing to pay (or cause them to pull out). 

If you still feel want to have spray foam insulation, make sure the company you use is going to properly assess the condition of the roof covering and structure prior to the installation, and study of the movement of air and moisture within the living and roof areas of the house. You should also ensure that they will be providing you with evidence they have done so, and have treated the roof properly (so that you have the evidence a surveyor will need to give your roof a clean bill of health). 

Proficiency and the RPSA both seek to promote best practice in all upgrade work carried out on properties.

Find out more about Proficiency at www.proficiency.services and the RPSA at www.rpsa.org.uk 

Ian Sturt, 11th March 2022