A class 1 vapor retarder is a material that has a perm rating of 0.1 perms or less. Examples of Class 1 Vapor Retarders. Materials used for moisture control that are considered class 1 vapor retarders include: Glass; Rubber Membrane; Polyethelene Sheeting; Sheet metal; Aluminum foil; These materials are used in different locations throughout ...

Apr 15, 2011 · Vapor Barrier: A Class I vapor retarder. The current International Building Code (and its derivative codes) defines a vapor retarder as 1.0 perm or less (using the same test procedure). In other words the current code definition of a vapor retarder is equivalent to the definition of a Class II Vapor Retarder proposed by the author.

Jan 26, 2018 · A Class I vapor retarder is a material with a permeance less than 0.1. That definition may be difficult to understand without some additional context. Permeance, for example, is the amount of moisture vapor that can pass from one side of an object (in this case a plastic liner/sheet) to the other.

Lstiburek proposed that there should be three classes of vapor retarders based on permeability as defined using the ASTM E-96 Test Method A (the desiccant method or dry cup method) and that a vapor barrier should be defined as a Class I vapor retarder.

Aug 28, 2024 · Class I barriers are the most impermeable, with a rating of 0.1 perms or less. They include materials like polyethylene sheets, rubber membranes, sheet metal, and glass, and they’re best for cold or humid climates.

Sheet polyethylene (visqueen) or unperforated aluminum foil (FSK) are Class I vapor retarders. Class II – Low permeability vapor retarders – rated greater than 0.1 perms and less than or equal to 1.0 perms. The kraft facing on batts qualify as a Class II vapor retarder.

The International Residential Code describes three classes of water vapor retarders: Class I vapor retarders (0.1 perms or less): Glass; Sheet metal; Polyethylene sheet; Rubber membrane; Class II vapor retarders (greater than 0.1 perms and less than or equal to 1.0 perms): Unfaced expanded or extruded polystyrene; 30 pound asphalt coated paper ...

The IRC requires Class I or Class II vapor retarders on the interior side of most above-grade frame walls in Climate Zones 5, 6, 7, 8, and Marine 4. It is permitted. Figure 2. Climate Zone Map (Source: DOE [1])

Vapor barriers are classified by their vapor permeance, or perm rating, which is a measure of the rate of moisture diffusion through the material. Class I vapor barriers have a vapor permeance of 0.1 perm or less. Class II vapor barriers have a vapor permeance of between 0.1 and 1.0 perm.

Apr 23, 2012 · If it’s really low, we call it a vapor barrier. The International Residential Code (IRC) updated its definition of vapor retarders in 2007 to include the three classes that Joe mentioned in his 2006 article. Class I: ≤ 0.1 perm (called impermeable) Class II: …