Dampsperren

Dampsperren are moisture barriers used in building envelopes to limit the diffusion of water vapor from indoor spaces into structural assemblies. By reducing vapor transfer, they help prevent condensation within walls, floors and roofs, which can lead to mold growth, material deterioration and reduced thermal performance. Dampsperren are typically part of a broader moisture-management strategy that also includes proper insulation, ventilation and air sealing.

Dampsperren can be classified as vapor barriers (low permeability) or vapor retarders (moderate permeability). They are commonly made as thin plastic films, foil-faced laminates, or multilayer polymer sheets. The choice between a barrier and a retarder depends on climate, building design and the desired balance between drying potential and vapor control. In many cases the barrier is placed on the warm side of the insulation to minimize vapor reaching colder areas where it could condense.

Installation requires careful attention to continuity and sealing. Seams must be tightly joined and reinforced with compatible tapes or sealants; penetrations for electrical, plumbing or ventilation must be properly sealed. The barrier should lie on the warm side of the insulation and should not create a hidden moisture trap behind it. Damaged sections should be repaired promptly.

Design and guidance vary by country and climate. Permeability is often described by Sd-values, with higher values allowing more drying of the building assembly. In cold climates interior damp barriers are common, whereas in milder or variable climates a vapor retarder with controlled permeability may be preferred to maintain drying potential.