BSD-106: Understanding Vapor Barriers | buildingscience.com
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.
What is a Class 1 Vapor Retarder - Crawl Space Ninja
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 ...
a vapor barrier should be defined as a Class I vapor retarder. At that time (2004) the International Building Code (and its derivative codes) defined a vapor retarder as 1.0 perm or less, equivalent to Lstiburek’s definition of a Class II vapor retarder. In the paper, Lstiburek provided examples of 14 different wall assemblies designed
Is a Class 1 Vapor Retarder Good Enough for Crawl Space Encapsulation?
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.
Vapor Barriers or Vapor Retarders | Department of Energy
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 ...
Moisture Control | Vapor Retarders- Installing, Perm Ratings
The IRC requires either a Class I or II vapor retarder on the interior side of frame walls in climate zones 5, 6, 7, 8 and Marine 4 (see climate zone map). A vapor retarder is not required for basement walls or on any portion of the wall that is below ground or on walls made of materials that can’t be damaged by moisture or by freezing.
Vapor Barriers and Vapor Retarders — What’s the Difference?
Class I vapor barrier/retarder: 0.1 perm or less; This covers most materials that are usually referred to as vapor barriers. When there is a 0.1 perm rating or less, the membrane is considered impermeable. Some examples to consider here are polyethylene film, glass, sheet metal, foil-faced insulated sheathing and nonperforated aluminum foil.
Vapor Barriers | Building Science Education
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.
Vapor Retarder? Vapor Barrier? Perms? What the Heck?!
Apr 23, 2012 · If the perm rating is low enough, we call the material a vapor retarder. 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)
10 Crawl Space Codes (2024 Requirements) - Home Inspector …
Dec 1, 2024 · Vent openings need to have a minimum of 1 square foot of area for every 150 square feet of crawlspace floor area. If there is a Class 1 vapor retarder on the crawlspace floor, this can be increased to 1 square foot of area for every 1,500-sf of floor area.
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