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What is a Class I vapor retarder?

Jim Brown

What is a Class I vapor retarder?

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.

How many vapor retarder classes are there?

three classes
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.

Is a vapor retarder of a certain class — Class I vapor retarder?

Water can enter a building as a liquid, a solid, as a vapor, and it can be adsorbed (that’s adsorbed with a “d”). a vapor retarder retards the movement of water by vapor diffusion; and. a vapor barrier is a vapor retarder of a certain class–Class I vapor retarder (see below for classes).

What is a vapor retarder in insulation?

Moisture Control: Utilizing Vapor Retarders. A vapor retarder is defined as a material or system that adequately retards the transmission of water vapor under specific conditions. The kraft facing on insulation is a vapor retarder. It can reduce moisture movement through your walls, floors, and ceilings.

What is the difference between a vapor retarder and a vapor barrier?

A vapor barrier is used during the construction of a building to prevent moisture damage to the building’s fabric. Vapor retarders are designed to impede moisture flow through the wall assembly and protect the building envelope from damage done by condensation.

Is vapor retarder the same as vapor barrier?

Which is an example of a Class III vapor retarder?

Class III vapor retarder 10 perms or less and greater than 1.0 perm This particular class has a permeance rating between 1 perm and 10 perms; as such they are also considered semi-permeable. Some examples include latex paints over gypsum board and #30 building paper and plywood.

What kind of vapor retarder do I need for my Batt?

The kraft facing on batts qualify as a Class II vapor retarder. Class III – Medium permeability vapor retarders – rated greater than 1.0 perms and less than or equal to 10 perms. Latex or enamel paint qualify as Class III vapor retarders. Climate zones for Class III Vapor Retarders

Can a vapor retarder be used in climate zone 2?

The IRC does not require or prohibit the use of vapor retarders in climate zones 1, 2, 3, and 4. NAIMA recommends using either a Class II or III vapor retarder in these warmer climate zones and avoid the use of Class I (very low perm) vapor retarders.

Can a vapor retarder be used on a latex wall?

Latex or enamel paint qualify as Class III vapor retarders. Class III vapor retarders can be used on the interior side of the wall in the following climate zones in any of the conditions outlined. The IRC does not require or prohibit the use of vapor retarders in climate zones 1, 2, 3, and 4.

What is a Class I vapor retarder?

Jim Brown

What is a Class I vapor retarder?

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.

What is an example of a class 3 vapor retarder?

Examples include unfaced expanded polystyrene, fiber faced polyisocyanurate and asphalt-backed kraft paper facing on fiber glass batt insulation. Class III vapor retarders have a permeance rating between 1 perm and 10 perms and are considered semi-permeable.

What qualifies as a vapor barrier?

A vapor barrier (or vapour barrier) is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies of buildings to prevent interstitial condensation and of packaging.

What is class 3 vapor retarder?

Class III vapor retarders have a permeance rating between 1 perm and 10 perms and are considered semi-permeable. This class includes most latex paints over gypsum board, #30 building paper and plywood. Any material with a permeance of over 10 perms is considered permeable.

What is a good air barrier?

A variety of materials make good air barriers. Some of the most common are drywall, plywood, polyethylene sheeting, oriented strand board (OSB) sheathing, and rigid foam insulation. Although air cannot leak through these materials, air can travel through openings and seams.

What are the different types of Vapor retarders?

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.

How are vapor barriers or vapor diffusion retarders measured?

The ability of a material to retard the diffusion of water vapor is measured in units known as “perms” or permeability. The International Residential Code describes three classes of water vapor retarders: Class I vapor retarders (0.1 perms or less): Class II vapor retarders (greater than 0.1 perms and less than or equal to 1.0 perms):

What is the International Building Code for 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 with the minimum vapor retarders proposed.

Can a vapor retarder be used on a latex wall?

Latex or enamel paint qualify as Class III vapor retarders. Class III vapor retarders can be used on the interior side of the wall in the following climate zones in any of the conditions outlined. The IRC does not require or prohibit the use of vapor retarders in climate zones 1, 2, 3, and 4.