Roof insulation questions, answered
Cost, methods, grants, standards and condensation in one place.
Free and no obligation. Your plan goes to one contractor, not a list.
- €1,800–€2,101attic floor, semi-D
- €2,000most attic grant
- 0.16W/m²K pitched roof
- 26counties
Plan your roof insulation
A few quick taps, and your plan fills in as you answer: the right method for your roof, what it costs, the grant and the standard to ask for. Contact details come last, and only if you want a contractor to price it.
Attic floor insulation, semi-d or end of terrace: €1,800 to €2,101 before the €1,500 SEAI grant, so about €300 to €601 to pay.
How the estimate is worked out
Attic floor insulation uses what SEAI-registered contractors were paid for each kind of home in 2026 and what an Irish installer charges, with the SEAI grant taken off. A room in the roof and a flat roof are priced per m² of the area you enter: rafter boards with a plasterboard finish, or a warm roof with a new membrane. VAT is included. Use it to plan with. It isn't a quote: a contractor prices your roof after a survey.
Where the insulation goes
Each roof in our drawings, with its own page: the method, the cost, the grant and what to watch for.
Attic insulationThe usual job: wool over the joists, a cold attic above, an SEAI grant towards it.
Rafter insulationBoards between and under the rafters, so the whole attic stays warm.
Room in the roofSloping ceilings, knee walls and a small top ceiling, wrapped all round.
Insulating from aboveBoards over the rafters when the slates come off anyway.
Flat roof insulationA warm roof on the deck, or a cold roof with a vented gap.
Garage and extension roofsFlat or pitched, heated or not: what each needs.Every question
How much does roof insulation cost in Ireland?
Insulating an attic floor costs €1,800 to €2,101 for a semi-detached house and €2,400 to €2,700 for a detached one, before an SEAI grant of €1,500 or €2,000. Insulating a room in the roof at the rafters, with a plasterboard finish, runs €100 to €180 per m², and a warm flat roof with a new membrane €130 to €190 per m². VAT is included.
Should I insulate the attic floor or the rafters?
Insulate where the warmth should stop. If the attic is only for storage, insulate the attic floor and keep the attic cold and ventilated. If people use the space under the roof, insulate at the rafters, all round the room. A flat roof is usually insulated on top of the deck as a warm roof, ideally when it is re-covered.
Is there a grant for roof insulation?
SEAI's individual grant for roof insulation is for the attic floor: €2,000 for a detached house, €1,500 for a semi-D or end of terrace, €1,400 for a mid-terrace and €1,100 for a top-floor apartment, with higher amounts for first-time buyers of an older home and some people on welfare payments. Rafter and room-in-roof insulation are grant-aided only as part of a One Stop Shop whole-home upgrade.
What U-value should a roof have?
For new work, the Building Regulations ask for 0.16 W/m²K in a pitched roof, whether it is insulated at the ceiling or along the slope, and 0.20 W/m²K in a flat roof. About 300 mm of mineral wool on an attic floor gets there.
How much does it cost to insulate a flat roof?
€130 to €190 per m² as a warm roof with a new membrane.
How much does rafter insulation cost?
€100 to €180 per m² for boards with an insulated plasterboard finish.
Is spray foam bad for a roof?
Fitted with no ventilated gap it can trap moisture and hide rot, and it is hard to remove. Have it surveyed.
Why is there condensation in my attic?
Usually blocked eaves vents or moist air leaking up through the ceiling. Ventilate the eaves and seal the ceiling.
How long does attic insulation take?
Most attic floors are done in a day.
What happens after I send my plan?
A single vetted insulation contractor for your area receives it with our estimate and calls to arrange a survey. The written price is yours to accept or turn down.
Every guide and county page
Methods
Costs, grants and rules
Keep the heat under your roof
Pick the roof, what's there now and the home to see the method and the cost. When you want a firm price, your plan goes to a single vetted insulation contractor for your area.