Ångspärrmembraner

Ångspärrmembraner, often referred to as vapor barriers or vapor retarders, are materials used in building construction to control the diffusion of water vapor. Their primary function is to prevent moisture from migrating through building envelopes, such as walls and roofs, and condensing within the structure. This condensation can lead to several problems, including mold growth, rot, and reduced insulation effectiveness, all of which can compromise the longevity and healthiness of a building.

These membranes are typically installed on the warm side of the insulation in colder climates. The warm side is the interior of the building during heating season, as warm indoor air holds more moisture. By placing the vapor barrier on this side, it blocks the passage of humid air from entering the colder parts of the wall or roof assembly. The specific placement and type of vapor control layer can vary depending on the climate, building design, and local building codes.

Common materials used for ångspärrmembraner include polyethylene sheeting, asphalt-coated paper, and specialized composite membranes. The permeability of a material is measured by its vapor permeance, which indicates how easily water vapor can pass through it. Materials are classified as vapor barriers (very low permeance) or vapor retarders (low permeance) based on these measurements. Proper installation is crucial for their effectiveness, ensuring a continuous barrier with all seams and penetrations meticulously sealed to prevent air leakage.