Höyrynsulkukalvot

Höyrynsulkukalvot, also known as vapor barriers or vapor retarders, are materials used in building construction to control the diffusion of water vapor through building envelopes. Their primary function is to prevent moisture from migrating from the warmer, more humid interior of a building to the colder, drier exterior. This is particularly important in climates with significant temperature differences between seasons, as condensation can form within wall or roof assemblies, leading to damage like mold growth, rot, and reduced insulation effectiveness.

These membranes are typically made from plastics, such as polyethylene, or coated papers. They are installed on the warm side of the insulation layer in walls, floors, and roofs. The placement is crucial; in cold climates, the vapor barrier is usually placed on the interior side of the insulation, while in hot and humid climates, it might be placed on the exterior side or an intelligent vapor retarder that changes its permeability based on humidity might be used. The permeability of a vapor retarder is measured by its vapor permeance, often expressed in perm units. Materials with lower perm values offer greater resistance to vapor diffusion.

Proper installation and sealing of vapor barriers are essential for their effectiveness. Gaps, tears, or poorly sealed joints can compromise the entire system, allowing moisture to bypass the barrier. Therefore, all seams and penetrations must be meticulously taped and sealed. The use and type of vapor barrier depend on local building codes, climate conditions, and the specific construction assembly.