Dampskydd

Dampskydd, often translated as vapor barrier or vapor retarder, is a material or system designed to restrict the movement of moisture vapor through a building assembly. Its primary purpose is to prevent condensation within walls, roofs, and floors. When warm, moist indoor air comes into contact with a colder surface within a building's structure, water vapor can condense into liquid water. This condensation can lead to various problems, including mold growth, rot, and degradation of building materials.

The effectiveness of a dampskydd is measured by its permeance, which is the rate at which water vapor can pass through it. Materials are classified into different classes based on their permeance values. Class I vapor retarders are the least permeable, essentially acting as vapor barriers, while Class III vapor retarders are the most permeable. The choice of dampskydd depends on the climate and the specific building assembly.

In cold climates, the dampskydd is typically installed on the warm side of the insulation, preventing indoor moisture from reaching cold surfaces within the wall. In hot and humid climates, the placement can be more complex, and sometimes a dampskydd is omitted or a more permeable material is used on the exterior. Proper installation is crucial for dampskydd to be effective, as any gaps or holes can allow moisture to bypass the barrier. Common materials used for dampskydd include polyethylene sheeting, foil-faced insulation, and certain types of paint.