We’ve just gone sale agreed and had our survey done. The surveyor’s report revealed that the attic has spray foam insulation in it. While the building surveyor said it wasn’t a total deal breaker, he did outline many issues with spray insulation. Should we be concerned about buying a property with this form of insulation in the attic? Is there anything that can be done to remedy it once it is in place?
In my early days as a surveyor in the 1990s when spray foam insulation was a new concept, a supplier asked me to review some properties for its installation. I have to admit, I didn’t like it, and I didn’t get it. Your question is forcing me to articulate why.
Assuming it’s an old house, spraying an attic can work, once it’s done properly. We all know that insulation reduces heat loss, maintains a more stable temperature and can lower heating bills. Spray foam has the added benefit of improved airtightness in an old attic. It also does not sag and drop out from the rafters overhead following light vibration, as might happen with traditional quilted insulation.
So, there are positives; but what are the pitfalls? Spray foam creates a seamless, airtight barrier. If not done properly, it could impede the cross-ventilation required to maintain the structural integrity of the roof timbers and to prevent their decay.
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In an older house, it can have the effect of strengthening the roof structure, in effect creating a raft effect with the rafters, thereby binding the roof together. Similarly, with slates and no felt underlining, where the original mortar protective layer known as ‘parging’ is missing, the spray foam can hold the slates in place. Fine, but it is only a temporary reprieve from a full roof replacement down the road.
The big downside is the impact that the spraying of a roof can have on the perceived market value of the property. Building surveyors remain wary of the effects of spray foam insulation for the reasons outlined above and tend to consider it as a proverbial blot on one’s report. Similarly, a valuation surveyor would take the view that having it materially decreases the market value of the property.
Another thing to consider is what happens when you remove such spray foam to enable refurbishment of an attic or to carry out basic roof repairs, for example. Spray foam can be difficult to remove without causing damage to any breather membranes under the roof covering or weak timbers in an older property.
So yes, you should be concerned. As you can see spray foam can lead to serious issues while removing it is not always straightforward and can be costly. It also has implications for the valuation of the property you are about to buy.
Before proceeding you should ascertain if:
- The previous owner used an SEAI-approved contractor.
- The contractor used open-cell or closed-cell spray foam. Open cell is probably best for Irish attics as it’s more breathable and will not trap moisture.
- That the contractor had a strategy to maintain ventilation by either maintaining a ventilated cold roof or designing a warm roof with a vapour control layer.
You should also get independent professional advice from a building surveyor or engineer familiar with this form of insulation.
When you have all that information to hand you will be able to make an informed decision on whether to proceed or not – and whether the agreed price should be reviewed.
For anyone else considering using spray foam I would recommend they follow the three steps outlined above. Also, they shouldn’t rule out the traditional methods of insulation with mineral wool or PIR board. These can often be cheaper and less destructive to an older roof.
Pat McGovern is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland
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