Diffuser membranes combine the properties of several films. As a waterproof material, they protect heat insulation and wooden constructions from water, at the same time protecting heat insulation from heat loss due to wind (blowing out).
Similar to wind insulation, they must have high water vapour permeability providing easy escape of moisture from within the roof constructions.
Material should be laid close to the heat insulation. If laid horizontally, make 10-15 cm overlaps. Overlaps should be taped using frost and moisture resistant adhesive tapes (e.g., Tyvek Tape or Gerband Outside DM Tape (386)). Leave a ventilation gap above the film.