Adding attic insulation: cost, savings and payback time in Sweden

Roughly 15 percent of the heat in a poorly insulated Swedish house escapes straight up through the attic floor. It is also the cheapest energy measure available for most houses.

Here is what the work costs, how large the saving is, and the moisture mistake that turns an energy upgrade into expensive damage.

How much insulation you need

The current recommendation for a cold attic in Sweden is 40 to 50 centimetres. Houses built before 1980 often have 10 to 20 centimetres, half of what is needed.

Measure in several places. Insulation settles and compacts over the years, and the depth at the gable says nothing about the middle.

Cost and savings

Blown loose-fill insulation typically costs 250 to 450 SEK per square metre installed. A 120 square metre attic therefore lands at 30,000 to 54,000 SEK before the ROT deduction on labour.

For a normal house on electric heating, the saving is 3,000 to 8,000 SEK a year at current prices. Payback is usually six to twelve years, and the insulation lasts at least fifty.

Moisture, the thing that actually goes wrong

Better insulation makes the attic colder, and colder air with the same moisture content means higher relative humidity. If the vapour barrier in the attic floor leaks, moist indoor air rises and can cause mould on the roof underside.

Seal every penetration for wiring, ventilation and the chimney before insulating, and make sure eaves ventilation is not blocked by the new loose fill.

The order that gives the best result

Do it in sequence: seal first, insulate second, review ventilation last. Never insulate over an attic with known leaks or damp stains, fix the roof first.

Always ask for a moisture measurement in the quote. Serious insulation firms document the moisture content of the roof trusses before starting.