A Class I vapor retarder is a material with a permeance less than 0.1. ... crawl space, with a liner of 0.1 perms allows over 4 gallons of moisture vapor to pass through in a year.Jan 26, 2018
What is a Class 1 or 2 vapor retarder?
Class I – Very low permeability vapor retarders – rated at 0.1 perms or less. ... 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.
What is a Class 2 Vapour barrier?
Class II. Class II vapor retarders have a permeance level between 0.1 perm and 1 perm and are considered semi-impermeable. Examples include unfaced expanded polystyrene, fiber faced polyisocyanurate and asphalt-backed kraft paper facing on fiber glass batt insulation.
What is a Type 1 air barrier?
Type 1 vapor barriers are very restrictive to moisture transmission, having a permeance less than or equal to 15 ng/(Pa·s·m2) of moisture passage. These barriers are required where there is cladding on the house that doesn't allow enough drying to the outside. ... Moisture management cannot depend on a vapor barrier alone.
What is a Class 1 vapor retarder material?
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.Jan 26, 2018
What is a Class I or II vapor retarder?
Class I – Very low permeability vapor retarders – rated at 0.1 perms or less. ... 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.
How is Vapour retarder installed?
For most of North America, vapor retarders should be installed in exterior walls on the warm-in-winter side of the insulation (toward the interior). For some warm and humid areas, such as Florida, the Gulf Coast and Hawaii, the vapor retarder should generally be installed facing the outside.
Is a vapor retarder of a certain class -- Class I vapor retarder?
a vapor barrier is a vapor retarder of a certain class--Class I vapor retarder (see below for classes).