A sweltering attic in summer — what actually helps?

An attic that becomes unbearably hot in summer is almost always a roof problem. The sun heats the roof tiles and the sheathing underneath for hours, and without insulation that heat radiates inward in the evening and at night — exactly when you want to sleep. Ventilating and blackout blinds help at the edges, but the core is the insulation value of the roof itself.

Insulation works both ways: the same layer that keeps heat in during winter keeps heat out in summer. For an attic you use as a room, that means insulating the sloped roof from the inside (€ 2,500 to € 8,000, roughly € 50 to € 100 per m²): insulation material against the roof slope, finished with board or plasterboard. The temperature difference on a hot day is large and immediately noticeable in the room where you sleep.

If you don't use the attic as a room but the heat radiates down into the bedrooms below, insulating the attic floor (€ 1,000 to € 2,500) can already help a lot — you keep the hot attic air above the floor and the level below cooler. It is the cheapest intervention and often done in a day. Which of the two suits your situation depends on what you do with the attic; read attic floor or roof slope.

After insulating, think about ventilation: the better the roof insulates, the more it matters that warm air can escape at night. A roof window that tilts open or mechanical extraction in the attic makes the difference between heat that lingers and heat that leaves. If you are not sure whether the roof, the attic floor or a dormer is the culprit, an insulation survey with thermal scan (€ 95 to € 250) reveals it. The bands per measure are in the price index.