I am installing ducts in the attic. Do they need to be insulated with a sleeve?

Yes, ducts located in cold zones must be insulated. This can be done either by using insulation sleeves or by covering the ducts with a minimum of 100 mm of blown insulation. If the space where the ducts are installed maintains a constant temperature above 15°C, it is normally not necessary to insulate supply and extract air ducts. However, outdoor air intake and exhaust air ducts must always be insulated along their entire length, regardless of temperature conditions, to prevent condensation and heat loss.