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Why spray foam insulation is bad news for homeowners

BY Ned Browne

29th Nov 2022 Home & Garden

Why spray foam insulation is bad news for homeowners

Spray foam insulation has been touted as an easy way to keep homes warm and insulated, but it comes with hidden costs that could affect your property's value

What is spray foam insulation?

Spray foam insulation is a liquid foam which is sprayed into position and then expands and sets into an insulating layer. It’s most commonly used on the underside of roofs, usually in a property’s loft space. 

On the face of it, this form of insulation seems to have many advantages. It can expand into every gap, it’s quick to apply and it was marketed as being able to prolong the life of an ageing roof (particularly one that pre-dated roofing felt).

So, what’s the problem?

Spray foam insulation in roofSpray foam insulation's airtight application may cause issues like damp in the roof

This form of insulation has been in use for 30 years but, in the last decade, the industry has grown rapidly, fuelled by online advertising showing short films highlighting the simplicity and effectiveness of the product.

The latter claim may be true, but the fact that spray foam insulation is airtight has also given rise to one of its issues: loft spaces, like all rooms in a property, need to breathe.

"The weight of the insulation has to be borne by the roof timbers, and they were not designed for this"

If no air circulates around the loft, this is highly likely to cause a build-up in condensation which can, in the long term, cause the roof timbers to rot.

Moreover, the weight of the insulation has to be borne by the roof timbers, and they were not designed for this.

But there’s also a bigger problem, one that could make the property unmortgageable, difficult to sell or not eligible for equity release.

You can’t inspect what you can’t see

When lenders carry out property surveys, the condition of the roof is a key factor. A leaking or damaged roof can lead to long-term structural issues and be expensive to repair.

"If the surveyor can’t inspect the roof because of the expanded foam, they are unable to complete their report"

If the surveyor can’t inspect the roof because of the expanded foam, they are unable to complete their report. This has led to underwriters refusing to lend on properties.

It’s also worth noting that surveyors will know about the possible condensation and weight issues. Some years ago, I wrote about zero value homes—at that time, it was mainly homes with external cladding and those with Japanese knotweed. You can now add spray foam insulated roofs to the list.

How many homes are affected?

Homeowner sits on sofa reading letter and looking anxiousThousands of homeowners will struggle to sell their homes because of spray foam insulation

It’s reckoned that 250,000 homes could be affected by spray foam insulation, and this number is rising every day, as the industry continues unchecked.

"250,000 homes could be affected by spray foam insulation"

In fact, up until March 31, 2021, this type of insulation was included in the Government’s Green Homes Grant (which was offered to homeowners). For some, this felt like a government seal of approval for spray foam insulation.

What can homeowners do?

If you are considering this form of insulation, please don’t sign on the dotted line. Tell your friends and family too.

If your roof is already spray foam insulated, you should employ a surveyor to get their professional opinion. Tell them you are concerned about possible condensation, rot, weight on the roof timbers, and mortgage/selling implications.

If their recommendation is to remove the insulation, you will probably find that it costs roughly double what it cost to install it—which is pretty galling.

A final thought: this issue is yet to be well documented. So, if you are affected, please write to your MP. More regulation to protect homeowners is urgently needed.

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