Room in the roof insulation
A room in the roof is insulated all round: boards between the rafters on the sloping ceilings, the knee walls at the sides, and the small flat ceiling at the top, finished in insulated plasterboard. It costs €100 to €180 per m² of those surfaces: about €3,000 to €5,400 for 30 m².
A converted attic or a dormer bedroom: how to wrap the room so it's warm in winter and not stifling in summer.
Free and no obligation. Your plan goes to one contractor, not a list.
- €3,000–€5,400for 30 m² of ceiling and walls
- 5%of BER roofs are rooms in the roof
- 3surfaces to wrap
- 0.16W/m²K to aim for
Wrap every side
- Sloping ceilings: boards between the rafters with the air gap kept, insulated plasterboard under.
- Knee walls: the short walls at the sides. The cold eaves space is behind them, so they need insulating like an outside wall.
- The top ceiling: the small flat ceiling under the ridge, insulated over the top like an attic floor.
- The floor of the eaves: where the eaves floor meets the rooms below, close the gap so cold air doesn't run under the room.
Cold spots to fix while the boards are off
Roof windows need insulated linings round them. Dormer cheeks and the dormer's own flat roof are insulated too: a cold dormer roof drips condensation into a warm room. Where a converted attic was finished years ago with thin insulation, it is often quicker to take down the plasterboard and start again than to add to it.
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.
Insulation for a room in the roof, 30 m²: €3,000 to €5,400.
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.
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.Questions before you insulate
How much does it cost to insulate a room in the roof?
€100 to €180 per m² of sloping ceiling, knee wall and top ceiling: €3,000 to €5,400 for 30 m².
Why is my attic room cold in winter and hot in summer?
Usually thin insulation in the slopes and knee walls, and gaps where they meet. Wrapping all three surfaces fixes both.
Is there a grant for room in roof insulation?
Only within a One Stop Shop whole-home upgrade.
Does a dormer need insulating separately?
Yes. Its cheeks and its flat roof are outside walls and a roof in their own right.
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.