Fugtbarrierer

Fugtbarrierer are building materials designed to limit the movement of water vapor and moisture through building assemblies. They are intended to reduce diffuse moisture transfer rather than to stop liquid water outright. In this sense, they are distinct from waterproofing membranes, which are designed to resist direct water infiltration.

There are two primary categories. Vapor barriers (or vapor retarders) have very low permeance and restrict vapor diffusion through walls, roofs, and floors. Damp-proof membranes (DPM) resist moisture to a lesser degree and are used in areas with lower moisture risk or where drying potential must be preserved. Common materials include high-density polyethylene sheets, foil-backed or laminated membranes, bituminous membranes, and specialized vapor-retarder paints or coatings. The exact material choice depends on climate, building type, and the desired balance between moisture resistance and drying potential.

Placement and installation are critical. In cold climates, vapor barriers are typically installed on the warm interior side of insulation or assembly to limit interior moisture from diffusing into the structure. In warmer, humid climates, the approach may differ to allow interior surfaces to dry. Regardless of type, barriers must be continuous and properly sealed around joints, penetrations, and edges to prevent gaps that can transport moisture. They should be compatible with other materials and not create unintended condensation within assemblies.

Limitations include the risk of trapping moisture or promoting mold growth if installed incorrectly or used in inappropriate climates. Moisture barriers are one component of moisture management, which also includes ventilation, drainage, and material selection to maintain healthy, durable building envelopes. See also vapor barrier, damp-proof membrane, and damp-proof course.