What is a Class 2 vapor retarder?
Class II vapor retarders are typically Kraft paper (Kraft-faced insulation). The permeance of Kraft paper increases to Class III levels at higher relative humidity (from 0.3 up to 3 perms).
What is class 1 or 2 vapor retarder?
Class I – Very low permeability vapor retarders – rated at 0.1 perms or less. 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.
Is an example of a Class III vapor retarder?
Class III vapor retarders (greater than 1 perm and less than or equal to 10 perms) include: gypsum board; fiberglass insulation (unfaced);
What is vapor retarder used for?
In most U.S. climates, vapor barriers, or — more accurately — vapor diffusion retarders (vapor retarders), should be part of a moisture control strategy for a home. A vapor retarder is a material that reduces the rate at which water vapor can move through a material.
What is class 2 Vapour barrier?
VAPOUR CONTROL MEMBRANE (VCM) CLASSIFICATION
Is Tyvek A vapor retarder?
No, DuPont™ Tyvek® is not a vapor barrier. It is made with unique material science to keep air and bulk water out while allowing moisture vapor inside walls to escape.
How many vapor retarder classes are there?
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.
Do I need vapor retarder?
If you live in a mixed climate – hot and humid with several heating months in the winter, you probably need a vapor retarder. Specifically, if you live in climate zones 4C (marine), 5, 6, 7 and 8.
What is a Class 4 vapour barrier?
Class 4 Vapour Permeable, Water Barrier and Air Permeable moisture control wall wrap. Advanced triple-layer construction. For use behind timber and fibre cement cladding. Also for use in cavity wall systems in climate zones 2*-8. Advanced water and vapour control membrane.
Is an example of a class I vapor retarder?
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.
Can Tyvek be stapled?
When staples without caps are used to temporarily fasten DuPont™ Tyvek® WRBs, no more than 4 staples per square yard should be installed. All staples should be sealed with DuPont™ Tyvek® Tape when the DuPont™ Tyvek® WRB is being installed for air barrier and high performance applications.
Do I need a vapor retarder?
Do I Need a Vapor Retarder? Vapor retarders are typically recommended for the interior side (i.e., the “warm in winter” side) of above-ground framed walls in your home, such as bedrooms, bathrooms, garages and attics.
What is the best vapor barrier for a crawl space?
Reduce Indoor Moisture. When you have high levels of indoor moisture,it’s typically because of crawl space concerns.
What is a Class A vapor barrier?
Types of Vapor Retarders. Vapor retarders are typically available as membranes or coatings.
What is 20 Mil vapor barrier?
The 20 mil crawl space vapor barrier is designed to protect the crawl space from outside moisture. Crawl space is the are that is most likely to develop mold and mildew due to excess moisture. Not only this damages the wooden floor, but it can also cause critical health hazards.