Dampenscherm

Dampenscherm is a moisture barrier used in building construction to limit the diffusion of water vapor through walls, roofs, and floors. Its primary function is to prevent interior moisture from migrating into insulation and structural layers where it can condense, reduce thermal efficiency, or promote mold growth and timber decay. In climate zones with cold winters, the dampenscherm is typically installed on the warm, interior side of the insulation and covered by interior finishes, though the exact position depends on climate and building design. In roofs it is usually placed under the interior ceiling; in walls it is placed behind the interior lining.

Materials and installation: Common dampenscherm materials include polyethylene sheets, aluminum foil laminates, or multi-layer vapor-retarder films with a specified vapor resistance (mu-value). Joints must be sealed and overlapped, and penetrations for pipes, cables, and outlets carefully taped. The barrier should be continuous to prevent vapor leaks; punctures should be repaired promptly. In some cases, a breathable, diffusion-open membrane may be used instead of a hard barrier to allow outward drying while preventing bulk water ingress.

Performance and limitations: A dampenscherm reduces the rate of vapor transfer but does not eliminate moisture production. Proper ventilation, humidity control, and correct placement are essential. If installed on the wrong side or damaged, it can trap moisture, leading to condensation, mold, and timber damage.

See also: Damp-proof course, Vapor barrier, Building envelope.