Spray Foam Insulation Under Your Roof: Checks for Dublin and Naas Homeowners

Spray foam insulation is sold as a quick way to make an attic warmer. Across Dublin City, North Dublin, South Dublin, Lucan, Bray, Wicklow and Naas, we regularly open attics where foam has been sprayed onto the underside of the roof, sometimes years ago by a previous owner.

Spray foam is not automatically a problem. A certified product, installed correctly with the right ventilation, can work. The trouble starts when foam is sprayed straight onto old felt, battens or slates with no ventilation gap and no paperwork. That can trap moisture against roof timbers, hide leaks, and make later roof repairs harder.

This guide explains what to look for, which documents to ask for, and what it means if you need roof work. It is general guidance. For a specific roof, get it inspected.

Why spray foam in a roof needs care

A traditional "cold roof" in an Irish house has insulation on the attic floor and a ventilated roof space above it. Air moves in at the eaves and out through vents, carrying away moisture that rises from the house. Our attic condensation guide covers how that works.

When insulation moves up to the rafters, the roof timbers sit inside a much smaller space. If that space is not ventilated, moisture can settle in the rafters and battens. SEAI's roof insulation ventilation bulletin (November 2024) warns that long-term interstitial condensation in a roof space can lead to roof timbers rotting.

Irish weather makes this more important. Long damp spells and wind-driven rain mean roof spaces around Dublin and Kildare rarely get a long dry season to recover.

What SEAI requires for grant-aided spray foam

SEAI's Better Energy Homes guidance is a useful benchmark even if your foam was not grant-aided. The same November 2024 bulletin says:

• Adequate ventilation is described as "a vital component" when spray foam is installed at rafter level.
• On SEAI grant-aided roof insulation jobs, only Irish Agrément certified spray foam products (or an NSAI-confirmed equivalent) are allowed.
• The foam must be installed in line with that product's Irish Agrément Certificate, which includes its ventilation requirements.
• In general, a breathable card is fitted between the rafters and the foam is sprayed onto the card, not onto the roof underlay. This keeps a continuous ventilation space between the foam and the felt or membrane.
• Where there are soffit vents, that ventilation space must connect to them so the roof gets cross-ventilation.

SEAI's economic feasibility bulletin (April 2025) adds that where spray foam is used, the NSAI Agrément Certificate or equivalent must be given to the homeowner.

In short, a well-installed job should leave you with a gap between foam and felt, vents that still work, and a certificate in your house file.

Signs of a spray foam installation that needs a closer look

You can check most of these from the attic hatch with a torch. Do not stand on the ceiling between joists, and never go onto the roof itself.

If the attic smells damp or you see wet patches, treat it the same as any suspected roof leak and get it looked at before winter storms.

Documents to ask for

If you installed the foam, or are buying a house that has it, try to gather:

• The product name and manufacturer.
• The NSAI Agrément Certificate (or equivalent) for that product.
• The installer's name and confirmation they were approved to install it.
• Any SEAI grant paperwork, if the work was grant-aided.
• Photos of the roof before and during installation.
• Any roof survey done before the foam went in.

Missing paperwork does not prove the job is bad, but it does mean someone will need to inspect it more carefully.

Buying or selling a house with spray foam

Spray foam has become a talking point in house sales. In the UK, RICS has published a consumer guide to spray foam insulation to help homeowners understand it.

In Ireland, policies vary, and we cannot tell you how a particular lender, valuer or buyer will react. Practical steps:

• Selling: have your certificate and installer details ready, and tell your solicitor early. Our seller roof inspection checklist covers what else to prepare.
• Buying: ask your surveyor to look at the attic specifically, and ask the seller for the documents above. See our pre-purchase roof inspection checklist.
• Either way: ask your lender or mortgage broker directly rather than relying on hearsay.

What spray foam means for roof repairs

This is where we see the biggest practical impact. When foam is bonded to the back of slates, tiles or felt:

• Replacing a few slipped slates can be awkward, because the slates and battens may be stuck to the foam.
• Finding a leak is harder. Water can travel along the foam before it shows on a ceiling, so the drip may be far from the actual defect.
• Checking the timbers may not be possible without removing some foam.
• Re-roofing usually means extra labour to strip foam from the rafters before new breathable membrane and battens go on.

Where foam has been sprayed onto a vent card with a clear gap behind it, repairs are usually far simpler, because the roof covering is still independent of the insulation.

We will always tell you what we can see before quoting, and whether a repair, a partial strip or a full roof replacement makes more sense.

Thinking of adding spray foam?

If you are considering spray foam for your attic, ask first:

1. Is the roof itself in good condition? Fix slipped slates, leaks and failing underlay before anything is covered up.
2. Is the product Irish Agrément certified, and is the installer approved to use it?
3. Will it be sprayed onto a breathable vent card with a ventilation gap, linked to eaves ventilation?
4. Would standard insulation at ceiling level, with good ventilation, do the job instead? It is often simpler to inspect and maintain.
5. If you want an SEAI grant, check the current requirements on seai.ie before work starts.

Get your roof checked

Perfect Roofing inspects and repairs roofs across Dublin City, North Dublin, South Dublin, Lucan, Bray, Wicklow, Naas and nearby areas. If you have spray foam in your attic and are worried about damp, leaks or upcoming roof work, we can check the roof, look at how the foam was installed, and explain your options in plain terms.

Contact us by WhatsApp, call 083 066 3462, or email hi@perfectroofing.ie. Photos of the attic taken safely from the hatch are a great help when you get in touch.