Dampbarrierer

Dampbarrierer are materials or assemblies used in building envelopes to limit the diffusion of water vapor and dampness through walls, floors, and ceilings. In many languages they are referred to as damp barriers or vapor barriers.

Their primary purpose is to reduce condensation, protect insulation, and prevent mold, rot, and corrosion by limiting moisture transfer from warm interior spaces to cooler building elements. The correct orientation and continuous coverage are important; in cold climates the barrier is usually placed on the warm interior side, while in very humid climates different strategies may apply.

Common types include sheet films made of polyethylene or polypropylene, foil-faced laminates, bituminous damp-proof membranes, and liquid-applied damp-proof coatings. Permeance and total resistance characteristics vary; low-permeance barriers provide greater moisture control but may require careful design to avoid trapping moisture.

Installation considerations include achieving a continuous, sealed layer with properly overlapped joints and penetrations sealed, avoiding punctures, and ensuring compatibility with other materials such as insulation and cladding. Damage during construction should be repaired with compatible tapes or patches.

Performance is described by permeance ratings or Sd-values, which indicate how easily water vapor can pass. In recent practice, breathable or vapor-permeable membranes are used where drying of the structure is desired; dampbarrierer are selected based on climate, building usage, and moisture risk. Damp barriers are not a substitute for good ventilation and drainage.