We have spray foam in our attic. We didn't think much of it at the time - the builder used it, it seemed like the modern choice, and we moved on. Then we started reading the UK news.
This guide lays out both options honestly - spray foam and rigid board (Kingspan/Xtratherm) - including the emerging risks that most contractor websites won't mention.
The two options, explained simply
There are two main ways to insulate an attic conversion in Ireland. Both work. But they have very different implications for your home's future.
Spray foam insulation
A liquid polyurethane foam sprayed directly between and onto the rafters. It expands, hardens, and bonds permanently to the timber and roofing felt. Better insulation per centimetre. More expensive. Two types:
Lower density, softer to the touch. Allows some moisture vapour to pass through, which means the roof structure can still "breathe" to a degree. This is the less problematic type. It's what we have.
Rigid board (Kingspan / Xtratherm)
Foil-backed PIR (polyisocyanurate) boards, cut and fitted between the rafters. Gaps are sealed with aluminium tape. A vapour barrier is installed on the warm side. Cheaper than spray foam. More labour-intensive to install. Well understood by lenders and surveyors. No mortgage issues anywhere. Can be removed if the roof ever needs repair.
The UK mortgage crisis - this is the important bit
UK mortgage warning
Over 250,000 UK properties have been affected by spray foam insulation issues. Major lenders are refusing mortgages on affected properties. This section explains what happened and why it matters for Irish homeowners.
In the UK, spray foam insulation has become a serious problem for homeowners trying to sell or remortgage. Here's what happened:
250,000+
UK properties affected
35%
of inspected properties had defects (PCA)
Major UK lenders refusing or restricting mortgages on spray foam properties include TSB, Skipton Building Society, Nationwide, Co-op, Principality, and Aviva. The list continues to grow. RICS (Royal Institution of Chartered Surveyors) has published guidance telling surveyors to flag all spray foam insulation during valuations.
Source: Elmhurst Energy - Lenders Continue to Reject Homes with Spray Foam (Jan 2025)
The Ireland situation - different, but watch this space
The good news: Irish banks have not adopted the UK stance as of 2025/26. Mortgages are still being approved on spray foam properties without issue.
From askaboutmoney.com
"Our house is spray foamed and we had no issues getting the re-mortgage done twice."
"Having gone through 4 different mortgage providers myself, I have never been asked anything about the roof."
There's an important practical point too: once your attic is fully converted, the spray foam is hidden behind plasterboard walls and in the sealed eaves spaces. It's not visible to surveyors during a standard valuation.
But here's why you should still pay attention. The UK and Ireland share many of the same lenders and the same RICS survey framework. A Northern Ireland surveyor has already told a buyer he'd advise "walking away" if spray foam was found. UK trends in property and lending have a habit of migrating to Ireland within a few years - and if you sell in 10-15 years, the lending landscape could look very different.
My honest assessment
We have open-cell spray foam - the more breathable, less problematic type. Day-to-day, it performs well. The attic is warm in winter, cool in summer, and our BER energy rating reflects that.
But if we were choosing today, knowing what we now know? We'd go with rigid board (Kingspan/Xtratherm). Not because spray foam doesn't work - it does. But because rigid board carries zero resale or mortgage risk, and that peace of mind is worth the trade-off. If you're selling, proper certificates and compliance documentation matter just as much.
Our recommendation
If you're choosing insulation for a new attic conversion, Kingspan or Xtratherm rigid board is the safer choice from a future resale and mortgage perspective. It's well understood, easily inspected, and causes no concerns for lenders or surveyors anywhere.
If you already have spray foam
Don't panic. Spray foam insulation works well and millions of homes have it installed without problems. But you should take a few precautions:
Find out (or ask your builder) exactly what product was used - brand name, spec sheet, and crucially whether it's open-cell or closed-cell. Keep this documentation safe. If you ever sell or remortgage, having the product spec and installer details could make the difference between a smooth sale and a blocked one.
What to ask your builder
Your builder's response to these questions will tell you a lot. A good builder will discuss the trade-offs openly. A builder who dismisses the concerns or insists on spray foam without explanation is waving a red flag.
"What insulation do you use?"
If they say spray foam, follow up with the questions below. If they use rigid board, you're in the clear.
"Open cell or closed cell?"
If they can't answer this immediately, that's a concern. They should know exactly what product they're installing in your home.
"Can you provide documentation and a spec sheet?"
You need the product name, manufacturer, and type on record. This protects you if lending rules change in Ireland.
"Are you aware of the UK mortgage issues with spray foam?"
A knowledgeable builder will know about this. If they brush it off or haven't heard of it, consider whether they're staying current on industry developments.
"Would you use Kingspan/rigid board if I asked?"
Any reputable builder should be willing to use rigid board if you request it. If they refuse or push back hard, ask yourself why.
Red flag
If a builder insists on spray foam, dismisses the UK mortgage concerns, or refuses to use rigid board when you ask - treat it as a red flag. A trustworthy builder will explain the trade-offs and respect your choice.
Side-by-side comparison
| Spray Foam | Rigid Board | |
|---|---|---|
| Insulation value | Better per cm | Good (slightly thicker needed) |
| Install speed | Fast (few hours) | Slower (cut & fit) |
| Cost | Higher | Lower |
| Gap sealing | Excellent (fills everything) | Good (needs taping) |
| Roof access for repairs | Difficult (bonded) | Easy (removable) |
| UK mortgage risk | High | None |
| Ireland mortgage risk | Low (for now) | None |
| Removability | Very difficult | Straightforward |
Common products used in Ireland
These are the rigid board products most commonly used in Irish attic conversions. Your builder should be familiar with both:
Kingspan Kooltherm K12 Framing Board
The most widely used rigid PIR board for attic conversions in Ireland. Foil-faced, excellent thermal performance, available in various thicknesses (50mm, 75mm, 100mm). Fits between timber rafters with aluminium tape at joints.
Xtratherm Thin-R Pitched Roof Board
An Irish-manufactured alternative to Kingspan. Same PIR technology, foil-faced. Often slightly cheaper. Equally well regarded by builders and meets the same building regulation requirements.
The bottom line
Spray foam insulation works. Millions of homes have it. But the risk landscape is changing, and the UK situation shows how quickly lending policy can shift. Ireland hasn't followed suit yet - but the trend is clear.
If you're getting an attic conversion done now, rigid board is the choice that gives you the best insulation with zero future risk. If your builder pushes spray foam without discussing the trade-offs, that tells you something about how they approach decisions that affect your home's value.
Worried about insulation choices?
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