Before you sign
External wall insulation problems, and how to avoid them
Most problems come from the details: window reveals, ground level, ventilation and sealant. Here's what goes wrong, why, and what to ask for.
Free, no obligation. One SEAI-registered contractor prices it, not five.
- €6,000SEAI grant, semi-D
- €6,000SEAI grant for a semi-D
- 150 mmmost homes can add without planning
Most external wall insulation problems come from detail and preparation, not the board: cold spots at window reveals, damp where the system meets the ground, poor ventilation after the house is sealed up, water getting in at cracked sealant, and walls left uninsulated. Each one is avoidable if you ask the right questions before you sign.
SEAI and NSAI both list the questions to ask, and they're below.
Does external wall insulation cause damp?
Done right, it shouldn't, and SEAI says a certified system can resolve rain penetration, poor airtightness and frost damage. SEAI still tells you to ask the contractor directly: "Will the system result in dampness in the walls?", "Will the system be at risk due to moisture absorbed where it comes into contact with the ground?" and "How will the insulation affect the breathability of the walls? Is there any risk of condensation?" (SEAI).
The common problems, and how to avoid them
| Problem | Why it happens | What to ask for |
|---|---|---|
| Cold spots and mould inside | Reveals, heads and cills left uninsulated, so heat escapes around the windows | NSAI: reveals, heads and cills must all be insulated |
| Condensation | The house is sealed up and the ventilation isn't checked | NSAI: the installer assesses ventilation before starting and tells you of any shortfall |
| Damp at the base | Insulation in contact with wet ground | SEAI's question about moisture where the system meets the ground |
| Water getting in | Sealant around windows and fittings cracks over time | NSAI: inspect sealants at least once a year and repair straight away |
| Walls left out | Only the front is done to save money | SEAI: every external wall, or no grant |
| Cracked render | Fixings drilled through the render afterwards | NSAI: fix external fittings only as the system maker says |
Why partial insulation is a problem
SEAI's quality alert says a whole-surface solution must be installed where physically and economically feasible, meaning all external heat-loss walls. A homeowner saying they can't afford it "is not an acceptable reason" to skip walls. Partial work is only accepted in exceptional circumstances, written on the Declaration of Works (SEAI, May 2024). Where some walls are cavity-filled and others wrapped, only one wall grant is paid, for the bigger area.
Uncertified systems and installers
NSAI says the system should hold a current Agrément certificate and the installer must be approved by NSAI to install that specific system. Get quotes only from contractors on NSAI's list of registered approved installers (NSAI). SEAI adds that if the contractor isn't on its register, you can't get the grant.
Walls that shouldn't be wrapped
NSAI lists timber frame, steel frame and timber-clad walls as unsuitable for external insulation systems. Old solid stone or brick homes built before about 1940 need a different approach, and SEAI's wall grants don't cover them under Better Energy Homes. See the grant page for the Traditional Homes pilot.
Nine questions SEAI says to ask
- Is the product suitable for my house?
- What thickness gets the wall to 0.27 W/m²K?
- Will it cause damp in the walls?
- Is it at risk from moisture where it meets the ground?
- How will it affect breathability, and is there a condensation risk?
- Will I need planning permission? Since 27 July 2026, usually not up to 150 mm. The 150 mm rule.
- Will it stop me painting or fixing things to the walls?
- Will you put back my gutters, pipes and satellite dish?
- Will I need an ESB Networks service alteration?
FAQ
Questions people ask
Does external wall insulation cause damp?
It shouldn't if it's a certified system fitted properly. SEAI says it can resolve rain penetration and frost damage, but tells you to ask the contractor about damp, ground moisture and condensation before you sign.
What are the main problems with external wall insulation?
Cold spots at uninsulated window reveals, condensation from poor ventilation, damp where the system meets the ground, water getting in at cracked sealant, and walls left uninsulated.
How do I maintain external wall insulation?
NSAI says inspect the sealants at least once a year, repair any damage straight away, and fix anything to the wall only the way the system maker says.
Can I wrap just the front of the house?
Not with the grant. SEAI requires every external wall to be fully insulated, and partial work is only accepted in exceptional circumstances.
Your grant
Your house wrap grant in 3 taps
Tap your home type, when it was built and any earlier wall grant. Your SEAI grant shows as you go. Then leave your number and one SEAI-registered external insulation contractor who covers your area rings you with a price.