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Solid walls · two jobs compared

Internal vs external wall insulation

For a solid or hollow block wall, internal insulation is the cheaper job and external the better one. On a semi-D, SEAI's medians leave about €6,343 to pay for internal and €17,219 for external after the grants (SEAI median costs). SEAI's own guide calls external insulation "the best way to insulate your walls" (SEAI wall insulation guide).

The grant, the cost, planning, room space and the outside of the house, side by side.

Get a free quoteCheck my grantFree. Your grant in 3 taps, then 4 questions for a price. One SEAI-registered contractor rings you.

Figures checked against SEAI and Citizens Information on 2 November 2026. wallinsulationgrants.ie is not SEAI or a government body and does not award grants.

The three wall insulation jobs SEAI grants, seen from above Three walls in section, outside on the left and the room on the right. Cavity wall: two leaves of block with the gap between them filled with insulation pumped in through drilled holes. Internal insulation, or dry lining: a solid wall with insulation board, a vapour control layer and plasterboard fixed to the inside face, so the room gets a little smaller. External insulation, or the wrap: a solid wall with insulation slabs fixed to the outside, covered with mesh and render, so nothing changes inside. Seen from above. Our drawing, not to scale. Cavity wallOUTSIDEROOMGap filled throughdrilled holes Internal (dry lining)OUTSIDEROOMBoard, vapour layer,plasterboard inside External (the wrap)OUTSIDEROOMSlabs, mesh andrender outside
The three jobs SEAI grants for walls, as its Homeowner's Guide to Wall Insulation describes them (SEAI). Which one a house can have depends on how its walls were built.
  • €8,000SEAI's fixed external wall grant for a detached house, the biggest of the three
  • €4,500for internal wall insulation (dry lining) on a detached house (SEAI)
  • €2,300the higher cavity grant for a detached house, for certain welfare recipients and HAP or RAS landlords (Citizens Information)
  • 24%of homes on the BER register with a known wall type have solid or hollow block walls: no cavity to fill (SEAI BER register)

FreeNo obligationOne contractor rings you, not fiveSEAI approves the grant before any work

Grant check

Your wall grant and what's left to pay

Three taps: the wall job, your home, and which rate fits you. The answer is SEAI's fixed grant and its own median cost for the job.

Wall job
Your home
Which fits you?

Your SEAI wall insulation grant

€3,500

SEAI median cost, Jan to Jun 2026
€9,843
Left to pay at the median
€6,343

SEAI's fixed internal (dry lining) grant for a semi-d or end of terrace at the standard rate is €3,500 (Citizens Information and SEAI, 2 November 2026). SEAI's median cost for that job on a semi-d or end of terrace, January to June 2026, was €9,843. €9,843 less €3,500 leaves about €6,343. Our sum; your quote can be higher or lower.

Send this for a real price
How this is worked out

The grant is SEAI's fixed amount for that wall job and home type, as SEAI's wall insulation page and Citizens Information (Citizens Information, updated 22 October 2026) list it. The higher rate applies to cavity walls only. The median cost is SEAI's own figure from grant-funded jobs completed between January and June 2026 (SEAI median costs); the PDF doesn't say whether VAT is in. Left to pay is the median less the grant, our sum. The home must have been built and lived in before 2011, every external wall must be done, the contractor must be on SEAI's register, and SEAI must approve the grant before work starts. It's an estimate, never a quote.

Side by side

Internal and external compared

Internal (dry lining)External (the wrap)
Grant, semi-D€3,500€6,000
Grant, detached€4,500€8,000
Median cost, semi-D€9,843€23,219
Left to pay, semi-D€6,343€17,219
Planning permissionNot neededMay be needed: protected structures, conservation areas
Room spaceSome lostNone lost
Outside of the houseUnchangedNew render finish
Meters and servicesWiring protected insideESB service alteration may be needed

Grants: SEAI. Costs: SEAI median costs; left to pay is our sum. Planning and services: seai.ie, SEAI. Room space and wiring: SEAI wall insulation guide.

Choose internal when

Internal suits

  • The front can't change: a protected structure, a conservation area, brick or stone you want to keep seen from the street.
  • The budget is closer to the internal figure.
  • You're redecorating or refitting the kitchen anyway, so the disruption inside is happening regardless.

Choose external when

External suits

  • You don't want to lose room space or move kitchens and radiators.
  • The walls let in rain, or the outside needs new render anyway. SEAI says certified external systems can deal with rain penetration, poor airtightness and frost damage (SEAI wall insulation guide).
  • You want the bigger grant on the bigger job.

housewrap.ie covers external insulation in detail.

Either way

The rules are the same

  • The home was built and lived in before 2011: SEAI goes by the date the electricity meter was installed (seai.ie). It needs an 11-digit MPRN.
  • Every external wall is insulated. SEAI does not grant part of a house.
  • One wall grant per home. A property that already had wall insulation through any government scheme can't get more for walls (seai.ie).
  • The contractor is on SEAI's register for that type of work, and SEAI approves the grant before materials are bought or work starts (Citizens Information).
  • A BER assessor rates the home after the work; SEAI adds €50 towards that BER.
  • If the work changes more than 25% of the home's outer surface, Building Regulations want the home to reach a B2 BER, or to have compliant heating and attic insulation (SEAI).

Your grant

Your wall grant and a price, in 4 taps

Tap your home, which wall job you think it needs, when it was built and which rate fits you. Then leave your number and one SEAI-registered insulation contractor who covers your area rings you to look at the walls and price it in writing.

What type of home is it?

SEAI pays a fixed amount for each type of home.

By sending, you agree to Wall Insulation Grants passing your details to one SEAI-registered insulation contractor who covers your area, so they can contact you about the job. wallinsulationgrants.ie is not SEAI or a government body and does not award grants. Privacy notice

FAQ

Questions people ask

Which is better, internal or external wall insulation?

SEAI's guide calls external insulation "the best way to insulate your walls" (SEAI wall insulation guide). Internal costs less and needs no planning permission (SEAI).

Can I do internal on some walls and external on others?

SEAI's pages don't say. Ask SEAI before you apply, and have the contractor confirm in writing which grant the job falls under.

Which grant is bigger?

External: €6,000 against €3,500 for a semi-D (SEAI).

Keep reading

Related guides

Where these numbers come from (6 public sources, checked 2 November 2026)
  1. SEAI, wall insulation grant page
  2. SEAI, individual energy upgrades: median costs and fixed grants, January to June 2026, 23,412 upgrades (PDF)
  3. SEAI, insulation grants page
  4. SEAI, Homeowner's Guide to Wall Insulation (PDF)
  5. Citizens Information, Better Energy Homes Scheme (page updated 22 October 2026)
  6. SEAI BER Research Tool, full public file (downloaded 29 October 2026, our sums)