Internal wall insulation, usually called dry lining, is the middle option. It costs less than wrapping the outside of the house and gets you a bigger grant than cavity fill. It is also the most disruptive of the three, because all of the work happens in your rooms.
| Upgrade | Apartment | Mid-terrace | Semi-D / end | Detached |
|---|---|---|---|---|
| Internal wall insulation (dry lining) | €1,500 | €2,000 | €3,500 | €4,500 |
SEAI fixed grant amounts, current at August 2026. Planning permission is not required for internal insulation.
€1,500 for an apartment, €2,000 mid-terrace, €3,500 semi-detached or end of terrace and €4,500 detached. That sits roughly halfway between the cavity and external grants, which is about right, because so does the cost.
As with every wall grant, SEAI requires a whole-surface solution. Every external wall of the home has to be insulated. That is the detail that catches people out on dry lining, because it means every room with an outside wall, not the two cold ones.
Planning permission is not required for internal insulation, which is one clear advantage over the external route.
Insulated plasterboard is fixed to the inside face of your external walls, then skimmed and decorated. Described that way it sounds simple. Here is the rest of it.
Skirting boards come off and go back on. Every socket and switch on an external wall has to be moved forward. Radiators come off the wall and go back. Curtain poles and blinds come down. Window boards and reveals have to be redone, and your window reveals get visibly deeper. Anything fixed to an external wall, including kitchen units and wall cabinets, has to be taken out and refitted. SEAI say this plainly in their own homeowner guidance.
You lose room space. Typically 60mm to 100mm off each external wall, which is not much in a large sitting room and is noticeable in a small bedroom or a narrow hallway.
For a whole house this is a job you either do while a room is empty, or one you plan around. Many people do it as part of a wider renovation, which is exactly when it makes most sense.
This is the honest weak point of internal insulation, and it deserves a straight answer. Once you insulate on the inside, the masonry wall behind the plasterboard becomes colder than it used to be, because your heat no longer reaches it. If warm moist air from the room gets in behind the board, it can condense on that cold surface where you cannot see it.
That is interstitial condensation. It is prevented by a vapour control layer on the warm side of the insulation, and it works, but only if it is continuous. The failures happen at joints, at the perimeter, and at every place somebody cuts a hole in it afterwards for a socket, a light fitting, a TV bracket or a shelf.
So ask your contractor three things. How is the vapour control layer sealed at the joints and edges. How are service penetrations sealed after the board goes up. And how are the reveals and the wall to floor and wall to ceiling junctions treated, because those are the cold bridges that show up as black mould in a corner if they are ignored.
One more thing that gets missed in older houses with suspended timber floors. The ends of the floor joists sit in the external wall, and that wall is now colder. Talk to the contractor about it before the work rather than after.
It suits hollow concrete block houses that cannot be pumped and where external insulation is too expensive. It suits mid-terrace houses where you cannot physically reach the party walls from outside anyway. It suits protected structures and homes in architectural conservation areas where you are not allowed to change the outside. And it suits anyone doing a full renovation, because the rooms are already stripped.
It suits you badly if the house is already tight on space, if the walls are damp, or if you cannot empty rooms.
If your walls have a fillable cavity, do that first. Cavity insulation is a fraction of the cost and a day's work, and taking it does not stop you dry lining or externally insulating later.
Dry lining is normally quoted per square metre of wall, and the make good work is where quotes diverge. Two contractors can quote the same rate per square metre and one includes moving the sockets, redecorating and refitting the kitchen and the other does not.
Get the quote broken into three parts. Insulation and boarding. Electrical and plumbing alterations. Making good, meaning skimming, skirting, reveals and decoration. Compare those three lines across quotes rather than the total.
Ask what the plan is for kitchens and built in wardrobes on external walls, because if that is excluded from the quote it is not excluded from the job.
Insulation you cannot see gets scored as if it is not there. This is not a theory. One homeowner was assessed at C1 rather than a likely B3 purely because the insulation in the house could not be verified on site. Another moved from D2 to B2 with no additional physical work at all, simply by getting a second BER assessment, after the first assessor recorded the wall insulation at half its actual thickness.
Dry lining is the measure most exposed to this, because the moment the skim coat goes on, the evidence disappears behind it.
So photograph everything. Photographs of the insulation boards in place with a tape measure in shot, the product labels, the delivery dockets, the datasheets and the contractor's written specification stating the thickness and the lambda value. Hand that pack to your assessor. It takes an hour and it is worth a grade. There is more on this in the BER guide.
External wall insulation performs better, because it wraps the whole house and covers the junctions where heat escapes. It costs roughly twice as much, needs planning checked, and carries a bigger grant.
Internal costs less, needs no planning, and can be done room by room in practice even though the grant needs all of it done. It takes space off your rooms, it needs careful vapour control, and it leaves cold bridges at floors, ceilings and party walls that external insulation would have covered.
If money and space are not the constraint, external is the better upgrade. If either one is, dry lining is a real option and not a consolation prize.
Your home must have been built and occupied before 31 December 2010 and have an MPRN. Grant approval has to be in place before work starts, the contractor must be SEAI registered for wall insulation, and a post-works BER is required before SEAI pays.
On second grants, the order matters. If you already had a cavity grant, you can apply for internal wall insulation now. If you take the internal grant, the only wall measure left to you afterwards is external. If you had external, there is no second wall measure at all.
You have eight months from your grant offer to complete the works, and 30 days to accept the offer in the first place. If the job runs on into a bigger renovation, that eight months arrives faster than you think.
Tell us your county and we will introduce SEAI registered wall insulation installers who cover your area.
€1,500 for an apartment, €2,000 mid-terrace, €3,500 semi-detached or end of terrace and €4,500 detached. It is a fixed amount regardless of what you are quoted.
Usually 60mm to 100mm off each external wall depending on the system and thickness. Barely noticeable in a large room, noticeable in a small bedroom or a narrow hall.
It can if the vapour control layer is not continuous, because the masonry behind the boards is now colder. It is prevented by proper sealing at joints, edges and every service penetration. Ask your contractor to explain exactly how they detail those before you sign, and do not insulate over a wall that is already damp.
No. SEAI confirm planning permission is not required for internal or cavity insulation. External wall insulation is the one that needs checking.
Yes. SEAI require a whole-surface solution, so every external wall must be insulated. Doing one or two rooms is not eligible, even though it is physically possible.
Yes. Internal first then external later is allowed as a second wall measure. The reverse is not. Once you have claimed external wall insulation you cannot claim another wall measure.
Only if you can prove it is there. Assessors score what they can verify, and hidden insulation with no evidence gets defaulted down. Photograph the boards in place with a tape measure, keep the product datasheets and dockets, and give the pack to your assessor.
Checked against the official pages on 27 August 2026. Grant terms change, so confirm current amounts with SEAI or your installer before you commit.