What the UK Government Has to Say
In March 2024 the Health and Safety Executive published a report. It contained research that assessed and identified the extent of moisture risk associated with the application of spray foam insulation when installed in timber, pitched roofs, when applied to roof tiles directly and when applied to roofs that incorporate a high resistance roof underlay like bitumen felt and modern vapour permeable roof underlays. The research they did on this used simulation modelling to assess condensation risks, timber decay and mould growth, considering climates in London and Newcastle, as well as the relevant British Standards.
While there has been some criticism in the spray foam industry for years over the methodology used, this research concluded that in all situations where open cell and close cell insulation was applied directly to the tiles, there was a high risk of timber degradation. In situations where the insulation was applied directly to the HR and LR underlays (with and without linings) the risks range between low and high for the degradation of the timber.
In our opinion, each individual case needs to be considered on its own merits, rather than generalised.
The research also indicates that the risks are lower when an open cell insulant (which is moisture permeable) is applied in accordance with the prescriptive roof constructions and guidance described in the British Standard BS 5250:2021. This is likely because these constructions include the provision of an air and vapour control later (AVCL) on the warm side of the insulation, as well as space left between the insulation and the roof underlay, which needs to be specifically ventilated in the case of high resistance underlays. For sprayed foam insulation, such spaces can be created by the use of card spacers, which are inserted between rafters or other similar techniques.
However, in practice this can be difficult to achieve without additional works to provide a sufficiently ventilated air gap. In our time we’ve seen some attempts to do this that haven’t been successful, and we’ve seen cardboard spacers deteriorate over time. The provision of the spacer might also reduce the depth of the insulation, which can be sprayed between the rafters.
How We Can Help
At Harrison Clarke we have extensive experience of inspective spray foam installations across the whole country. Our experts are able to check for issues, determine the compliance with manufacturers certifications, and report back to you on the installations themselves.
We also have years of experience inspecting properties after spray foam insulation has been removed to provide reassurance for mortgage or equity release providers. We can even inspect beforehand to provide proof where installations appear to be satisfactory and no remedial work is needed. After all, removal might not always be necessary! We’ve also been instructed by legal firms to provide evidence where installations haven’t been done correctly. In these situations, our legal contacts may be able to help you pursue a claim to recover the costs of installation and/or removal, particularly if the payment was made for all or part of the works using a credit card.
So if you need any help or advice on spray foam insulation, we’re the right people to speak to! Our team of experienced surveyors are on hand to answer any of your questions and discuss your situation, so please feel free to call us on 023 8155 0051. We look forward to helping you.
For more expert advice on surveying and property matters, check out our range of informative videos on our website or YouTube channel. Harrison Clarke Chartered Surveyors is here to guide you every step of the way!
At the time of writing, we have a total of 129 reviews across Trustpilot and Google. We are proud to say that the average rating is over 4.9/5.
