treated paper or plastic that is either attached to insulation or plastic that is placed over unfaced, installed insulation to keep the moisture in the air from condensing in the insulated cavity.
a material or coating, impermeable to moisture, designed to impede passage of water or water vapor.
a material or structural element that can be used to inhibit the movement of water vapor, while an air retarder can inhibit airflow, into and out of a house 's envelope
a material that has a flow rating of one perm or less
a material that restricts or reduces the rate and volume of water vapor diffusion through the ceilings, walls, and floors of a building
A material with a high resistance to vapor movement, such as foil, plastic film, or specially coated paper, that is used to control condensation or prevent migration of moisture.
A material which retards the transmission of water vapor. It is rated in perms ("permeance"). The lower the perm rating, the better the water vapor permeance. A vapor retarder should have a perm rating no greater than 1.0.
A component that retards water vapor diffusion but does not totally prevent its transmission. Vapor retarder material is usually a thin sheet or coating. However, a construction of several materials, some perhaps of substantial thickness, could also constitute a vapor retarder system.
Helps control the amount of moisture passing through the insulation and collecting inside exterior walls, ceilings and floors.
A material that reduces the diffusion of water vapor across a building assembly.
Any substance that prevents the transmission of water vapor.
Material which, when installed on the high vapor pressure (warm in winter) side of a material, retards the passage of moisture vapor to the lower pressure (cold in winter) side. Note exception: Florida and Gulf Coast. Check local building codes to determine what side the vapor retarder should be placed.
A vapor retarder is the element that is designed and installed in an assembly to retard the movement of water by vapor diffusion. There are several classes of vapor retarders: Class I vapor retarder - 0.1 perm or less Class II vapor retarder - 1.0 perm or less and greater than 0.1 perm Class III vapor retarder - 10 perms or less and greater than1.0 perm The test procedure for classifying vapor retarders is ASTM E-96 Test Method A - the desiccant or dry cup method.
A material that impedes the transmission of water vapor under specified conditions.
(1) A sheet material designed to restrict the passage of water vapor through a roof or wall. In the roofing industry, a vapor retarder should have a perm rating of 0.5 or less; (2) Roof component designed to obstruct water vapor flow through a roof or wall; (3) Any material used to prevent the passage of water vapor; (4) Material installed to impede or restrict the passage of water vapor through a roof assembly. See VAPOR BARRIER.
Any material used to prevent the passage of water vapor. Applied to insulation or other surfaces, it retards vapor travel to regions of low temperature where it may condense. A material is considered a vapor retarder if it has a perm rating of 1 or less (the lower perm, the better the vapor retarder). Examples: Kraft facing on insulation, foil facing on insulation.
Those materials or systems that retard the transmission of vapor under specified conditions.
Any material used to prevent the passage of water vapor. Vent: Any outlet for air that protrudes through the roof deck such as a pipe or stack. Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck.
Material used to slow the flow of water vapor through walls and other spaces where this vapor may condense at a lower temperature. Typically used to prevent undesired condensation in an area.
A material that retards the movement of water vapor through a building element (walls, ceilings) and prevents insulation and structural wood from becoming damp and metals from corroding. Often applied to insulation batts or separately in the form of treated papers, plastic sheets, and metallic foils.