The perils of spray foam insulation
If you believe the manufacturers, spray foam insulation is something of a miracle cure for issues in your roofspace. The reported benefits include preventing tiles and slates from slipping by securing them in place, and improving roof insulation to help avoid water tanks and pipes freezing. It is also claimed that spray foam can assist in keeping your loft space clean and dry, that it is quick and easy to apply and that it is environmentally friendly.
Raphael Stipic, owner of Anglian Home Surveyors, urges homeowners to be wary, however. ‘As experienced building surveyors in Cambridge we would encourage homeowners to exercise caution before resorting to spray foam insulation,’ says Raphael. ‘The main area of concern is the effectiveness with which the spray foam can insulate, with the result that if any rain does manage to come through the roof, it will be held by the foam, potentially causing excess damp and even the rotting of roof trusses, battens and purlins.
‘Spray foam also increases the possibility of interstitial condensation. This occurs when the difference in temperature between the inside and outside is great enough to cause condensation where the insulation meets the roof covering. There is nowhere for this condensation to escape so there is a risk of rotting timber. A normal roof will breathe naturally and is open for inspection should there be a problem. In extreme circumstances we have heard of mortgage companies refusing to lend against properties that have spray foam insulation. All in all, we’d recommend avoiding it altogether and if you’re in any doubt it’s advisable to consult a building surveyor for advice.’
It is common knowledge that listed buildings can prove to be something of a challenge, not only in terms of maintenance but also in terms of the cost of keeping them warm in winter. Spray foam insulation can appear to be a convenient solution in both cases, but it is important to remember that listed buildings tend to have roofs constructed using handmade clay tiles originally fixed with an oak peg or tiles that are nailed down. Should the tiles become displaced for any reason, or the nails rust and allow water to permeate, the level of damp can be exacerbated. And in a worst case scenario, should you need to have extensive work done on the roof, or even replace it altogether, it is likely that the roof tiles will have stuck to the spray foam and been rendered unusable.
Anglian Home Surveyors are building surveyors in Cambridge and Haverhill. If you’re considering buying a property, building a new home or extending an existing house, or if you have any concerns at all about spray foam insulation, why not contact us to commission a full building survey?
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