Niiskuskaitsebarjäär

Niiskuskaitsebarjäär, often referred to as a vapor barrier or moisture barrier, is a material or membrane used in construction to prevent or control the passage of water vapor. Its primary function is to inhibit moisture from migrating through building assemblies, such as walls, floors, and roofs. This is crucial for maintaining the integrity of building materials, preventing mold growth, and ensuring indoor air quality.

Vapor barriers are typically installed on the warm side of the insulation in a building envelope. The "warm side" is the side that will be warmer during the heating season in cold climates, or the side that will be warmer during the cooling season in hot climates. This placement is critical to prevent condensation from forming within the wall or roof structure when warm, moist indoor air comes into contact with colder surfaces. Common materials used for vapor barriers include polyethylene sheeting, foil-faced insulation, and certain types of paints and coatings.

The effectiveness of a vapor barrier is measured by its permeance, which indicates how easily water vapor can pass through it. Materials with very low permeance are considered vapor barriers, while those with higher permeance are classified as vapor retarders. The choice between a vapor barrier and a vapor retarder depends on the climate and the specific building assembly. In very cold climates, a more robust vapor barrier is generally required. Improper installation, such as tears or gaps in the material, can significantly reduce the effectiveness of a vapor barrier, leading to potential moisture-related problems.