vaporbarrier

A vapor barrier, also known as a vapor retarder, is a material used in building construction to prevent or slow the diffusion of water vapor through a material or assembly. Its purpose is to control the movement of moisture within walls, ceilings, and floors, thereby preventing condensation that can lead to mold, rot, and structural damage. Vapor barriers are typically installed on the warm side of the insulation in colder climates and on the cool side in warmer climates, depending on the direction of vapor drive. Common materials used as vapor barriers include polyethylene sheeting, aluminum foil, and certain paints or coatings. The effectiveness of a vapor barrier is measured by its permeance, with lower permeance indicating a greater ability to resist vapor flow. Proper installation is crucial for a vapor barrier to function effectively, ensuring there are no gaps or tears that could allow moisture to bypass the barrier. Building codes often specify requirements for vapor barriers based on climate zone and building type.