Cavity wall insulation questions

SEAI pays €1,800 for a detached house, €1,300 for a semi-D or end of terrace, €850 for a mid-terrace and €700 for an apartment (seai.ie, checked 28 October 2026). Homeowners on a qualifying welfare payment, and homes in an active HAP tenancy or RAS arrangement, get €2,300, €1,700, €1,100 and €900.

SEAI's median installed cost in the first half of 2025 was €1,500 for a semi-D and €2,250 for a detached house, VAT included (as published by saveonheat.ie). After the grant, that's about €200 for a semi-D and €450 for a detached house.

Homes built and occupied before 31 December 2010, with an MPRN, using an SEAI-registered contractor, with a grant offer before work starts, and all external walls fully insulated. Partial insulation isn't eligible (seai.ie).

Yes. Work done before SEAI approves and you accept the grant offer isn't funded.

Usually one day for a house. The contractor drills a pattern of small holes in the outer wall, pumps the insulation in and fills the holes to match.

Most of the work is outside. Someone may need to look at vents inside. The drilled holes are filled to match the wall.

No. SEAI says planning permission is not required for internal or cavity insulation (seai.ie).

No. Solid walls and timber frame walls can't be filled, and a wall with damp problems needs fixing first. See is my house suitable?

You may apply for a second wall insulation measure. After a cavity grant: internal or external insulation. After internal: external only. After external: none. A second cavity grant isn't available.

Usually, if the cavity was empty. Less heat leaks out through the walls, so rooms hold their heat longer and the heating runs less. How much you notice depends on the house, the heating and how warm you keep it.

It usually improves it, because the walls lose less heat. A BER assessor can tell you by how much for your home.

No. SEAI pays a fixed amount by home type, whatever the quote. Compare the price you're quoted with SEAI's median cost.

No. The grant is only paid when an SEAI-registered contractor does the work. Cavity filling needs a pump and a trained installer anyway.

It's how fast heat passes through the wall. The lower the number, the less heat escapes. For the grant, the insulated wall must reach 0.27 W/m²K or lower, so ask the installer if the product will.

Your Meter Point Reference Number, on your electricity bill. SEAI uses it to identify the home and to see what grants it has had before.

We pass your request to one SEAI-registered contractor who covers your area. For the grant, the contractor must be on SEAI's register. They ring you, check the walls and give you a price. Nothing is booked until you say yes.

No. cavitywallinsulation.ie is not SEAI or a government body and does not award grants. We pass your request to a contractor. You apply to SEAI for the grant yourself, or the contractor helps you with it.

No. The grant check and the callback are free to you.