Cavity wall insulation cost in Ireland
Cavity wall insulation costs a median of €2,250 for a detached house in Ireland, €1,550 for a semi-detached or end of terrace, €1,100 for a mid terrace and €950for an apartment.After the SEAI grant, a detached house typically pays about €450.
Cavity wall insulation injects bonded bead or foam into the gap between the inner and outer leaf of the wall. It is only possible where the house was built with a cavity.
| House type | Median cost | SEAI grant | You pay |
|---|---|---|---|
| Detached | €2,250 | −€1,800 | €450 |
| Semi-detached or end of terrace | €1,550 | −€1,300 | €250 |
| Mid terrace | €1,100 | −€850 | €250 |
| Apartment | €950 | −€700 | €250 |
SEAI, Better Energy Homes and Solar PV: individual energy upgrades costs and grants.47,067 energy upgrades completed through the Better Energy Homes and Solar PV Scheme, January to December 2025. Checked 2026-08-13.
What the median does not tell you
- Cavity insulation is by a wide margin the cheapest way to insulate a wall: €2,250 for a detached house against €24,980 for external insulation. Where the house has a fillable cavity it is normally the first wall measure to consider.
- The grant covers a large share of the cost. A detached house at the median pays €2,250 and can claim €1,800, which is the highest grant-to-cost ratio of any measure here.
Treat this as a sense-check, not a quote
A median is the mid-point. Half the homes in SEAI's sample paid less than €2,250and half paid more. What you are quoted depends on the size and condition of your home, and on what the contractor finds when they survey it. Get more than one quote.
The grant that pays towards this
The SEAI Cavity Wall Insulation grant is worth up to €1,800. Available for homes with cavity walls built and occupied before 2011.
The grant is paid after the work is finished, and only when the work is carried out by a contractor on the SEAI register. You pay the contractor in full first.
Full detail on the Cavity Wall Insulation grant →See what your own home qualifies for
Answer a few questions about the house and get the grant total for this upgrade and every other one it is eligible for. We email you the contractor contacts to approach yourself, and we do not share your details with them.
Cavity wall insulation contractors by county
137 SEAI-registered contractorsacross 26 counties do this work, and the grant is only paid when the work is done by one of them. A business covering several counties appears in each of them.
Common questions
How much does cavity wall insulation cost in Ireland?
The median cost is €2,250 for a detached house, €1,550 for a semi-detached or end of terrace house, €1,100 for a mid terrace and €950 for an apartment. These are SEAI's published medians for January to December 2025.
What does cavity wall insulation cost after the SEAI grant?
A detached house at the median pays €2,250 and can claim €1,800, leaving about €450. The grant is paid to you after the work is completed by an SEAI-registered contractor, so you pay the full amount up front.
Is this the price I will be quoted?
No. A median is the mid-point: half of the upgrades in SEAI's sample cost less than €2,250 and half cost more. Your quote depends on the size and condition of your home and on what the contractor finds when they survey it. Use the median to sense-check a quote, not to predict it.
Who can carry out cavity wall insulation under the grant?
Only a contractor on the SEAI register. Qualified.ie lists 137 registered contractors who do this work, across 26 counties.