Spray Foam Insulation In Loft Is Bad News
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Spray Foam Insulation In Roof Is Bad News

After a lot of house hunting, I eventually found a property that I was interested in buying. As part of the buying process, I got a survey done on the property. The survey showed that the house was generally in good shape but highlighted that the roof had spray foam insulation. Initially, I didn’t think this was much of a concern until I spoke with my conveyancer. It turns out spray foam insulation is very bad news!

What Is Spray Foam Insulation

Spray foam insulation is exactly what the name suggests; it’s spray foam that is used for insulation. It looks a lot like the expanding foam that’s often used in DIY.

There are two types of spray foam insulation:

Open Cell Foam

Open-cell spray foam insulation is a type of building insulation that expands to fill spaces, creating a thermal barrier.

It is called “open cell” because its foam structure is made of tiny cells that are not completely closed, making it softer and more flexible than closed-cell foam. This insulation is less dense, offers good thermal insulation, is permeable to air and moisture, and is excellent for sound absorption.

Open-cell foam is generally more affordable than closed-cell foam. It is applied as a liquid that expands, making it effective for insulating hard-to-reach areas.

Closed Cell Foam

Closed-cell foam insulation is very similar to open-cell foam insulation, but it has a higher density and compact cell structure, giving it better insulation properties compared to open-cell foam.

Because it is dense, closed-cell foam is better at blocking air and moisture. It is also sometimes used as a quick and cheap way of adding structural integrity.

What Is The Problem With Using Spray Foam Insulation In A Roof

There are several problems with using spray foam insulation in the roof space. In my situation the main concerns were:

  1. Moisture Trapping: Spray foam can trap moisture against the roof deck, potentially leading to wood rot and mould growth. This is particularly problematic in homes where the roof might not have a proper vapour barrier.

  2. Ventilation Issues: Proper roof ventilation is crucial for managing moisture and temperature. Spray foam insulation can block ventilation paths, increasing heat and moisture accumulation.

  3. Structural Problems: It is not uncommon for people to repair a roof that is starting to fail by using foam insulation to add additional structural integrity. Clearly, using spray foam insulation to hold up a roof is not good.
Spray Foam Insulation In The Roof
Spray Foam Insulation In The Roof

Spray Foam Insulation Means You Can NOT Get A Mortgage In The UK

Nearly all UK lenders will not approve a mortgage on a house that has spray foam insulation in the roof space!

Some UK mortgage lenders will currently lend if the spray foam insulation is open cell and all the paperwork for its installation is available.

My lender was one of the many who would not lend if spray foam insulation had been installed in the roof space. My lender didn’t perform a survey to check for the spray foam, but the fact my survey did find the spray foam insulation meant that my conveyancer had to inform my lender as it was part of the loan agreement terms and conditions. 

IMPORTANT: It is worth considering that in the future, no UK mortgage lender will approve a mortgage on a house with spray foam insulation in the roof. This would make it very difficult to sell a property with foam insulation.

How To Remove Spray Foam Insulation From A Roof

Unfortunately, it turns out that removing the spray foam insulation is a much bigger task than installing it. This is because it sticks like glue to everything it’s sprayed on. Making removal difficult and very likely to cause damage to whatever surface it has been sprayed onto.  

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There are a number of different options when it comes to removing the foam, but the most effective (and the most expensive) option is to get a roofing company to remove the roof, clean out all the foam, and put the roof back.

This is the best option because any damage the foam has already caused (e.g., rotted wood) and any damage caused by removing the foam can be fixed simultaneously.

Obviously, removing a house roof is a fairly major undertaking. Below are the time and costs to remove the foam from the property I was looking at buying (a 3-bed semi-detached).

 – The total job cost £12,000 (including VAT)
 -The surveyor to inspect the roof after the foam is removed cost £300 (including VAT)

1 day  – For the scaffolding to go up
5 days –  Take the roof off, remove the foam, replace roof battens, repair a rafter, install a new breathable membrane and put the roof back on
1 day – Takedown scaffolding 

Fortunately for me, the foam had only damaged a small section of a rafter, which the roofers easily fixed.

Potentially, the foam could have damaged the main structural wood supports, which would have meant more expense.

RICS Home Survey Report

Below is a copy of the section in my RICS home survey report that talks about the spray foam insulation in the roof

Roof structure
Limitations on the inspection
The roof void could not be fully inspected because of insulation and spray foam present. As a result, there are areas upon which I cannot report.

Description of the element
The roof is of timber and is formed in prefabricated trusses. The roof void is fitted with fibreglass and foam insulation. The firewall is of masonry construction.

Condition and recommendation
Spray foam insulation has been applied to the underside of the roof slopes. This conceals the roof timbers and linings restricts ventilation and can cause accelerated rot and decay of hidden areas. It is not possible to determine if the roof timbers and fixings to this property have been affected. The type of insulation has not been determined. This installation should, therefore be regarded as suspect and you should ask your legal adviser to make further enquiries in this respect. Further advice on this subject can be obtained from the Property Care Association www.property-care.org. However, you should budget for the replacement of the roof covering.

Condition Rating 3.

If you want to find out more about spray foam insulation, then I recommend you download the PDF document that can be found on the RICS website.

Conclusion: Spray Foam Insulation In The Roof Is Bad News

Apparently, spray foam insulation works very well at keeping the heat in your house. Unfortunately, as I found out, the spray foam also works very well at making a property unmortgageable and potentially damaging your roof.

My experience is that spray foam insulation in the loft of a UK semi-detached house is very bad news. 


FAQ: Spray Foam Insulation

Which mortgage lenders accept spray foam insulation?

It is best to assume that no UK lenders will offer a mortgage on a property with spray foam insulation in the roof space.

Fewer and fewer lenders are offering mortgages on properties with spray foam insulation. There will probably come a point when no one will lend on a property with spray foam insulation. So even if you can get a mortgage today, when you come to sell the house in a few years, it might not be possible for any potential buyers to get a mortgage.

What is spray foam insulation?

Spray foam insulation is a chemical product created by mixing and reacting two materials to form foam. This foam expands upon application, filling gaps, cracks, and spaces, providing an effective insulation layer. 

Why use spray foam in the roof space?

  • Energy Efficiency: It creates a tight seal that can significantly reduce heat loss, leading to lower heating costs. 

  • Air Sealing: It effectively seals air leaks, preventing drafts

  • Structural Integrity: Closed-cell foam can add to the structural integrity of the roof and building. Using foam in this way is a bodge job, as the foam is not designed for this purpose.

  • Soundproofing: Spray foam has excellent soundproofing properties

How long does spray foam insulation last?

When properly installed, spray foam insulation can last over 25 years. It does not settle or sag over time, maintaining its insulation properties for decades.

Is spray foam insulation safe?

Once cured, spray foam insulation is generally considered safe. During application, it releases chemicals that can be harmful if inhaled. 

Should I use spray foam insulation in my roof space?

It works very well as an insulator, better than the standard stuff used in UK lofts. However, it has the potential to severely damage the wood and other components that make up the roof. In the UK, most lenders will not offer a mortgage to a house with spray foam due to the potential damage it can cause.

Where can spray foam insulation be used?

Spray foam insulation can be used pretty much anywhere that needs insulating. 

Can I sell my house with spray foam insulation?

Selling a house in the UK with spray foam insulation is going to be difficult. UK lenders don’t like offering mortgages with properties that have spray foam insulation.

How do I know if my house has spray foam insulation?

Take a look in your loft. If you see white foam stuck to the roof, it is probably spray foam. 

Will a home survey identify spray foam insulation?

Yes, a home buyer survey includes the type of roof insulation in a property. 


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