Most vapour retarders consist of 1- to 3-layer films made of polyethylene (PE), polypropylene (PP) or polyamide (PA). In some cases, fleece laminations are attached, which on the one hand have a moisture-regulating effect, and on the other hand serve as a protective layer between the foil and the wooden formwork in the case of above-rafter insulation. The incorporation of mesh meshes increases the tear resistance of the films. They are usually laid loosely, and the connections and transition areas are glued with the corresponding adhesive tapes. Since their Sd value only has a diffusion-inhibiting effect, it must be ensured that the overlying layers are more diffusion-open than the vapour barrier and thus allow moisture to dry out. For this purpose, either a tested system structure of the manufacturer should be available or a mathematical proof should be provided.
Source: bauwion
