XI. INSULATION PRODUCTS

A. Kraft Faced Insulation
Three accepted methods of installing faced insulation are inset stapling, face stapling, and pressure fit - no stapling. The vapor permeance of a wall is not significantly affected by any one of these methods.

B. Polyethylene Sheet or Foil Vapor Retarder
Separate vapor retarders are used in some applications. When required, a separate vapor retarder should be installed at the warm in winter side of the framing. In hot, humid climates, vapor retarders are sometimes omitted or installed outside the insulation.

C. Ground Covers
Where the floor of a crawl space is soil or gravel, a ground cover should be used to limit the evaporation of water moving from damp soil into a crawl space. It is recommended that a ground cover be 4 mil or thicker polyethylene sheet or 55 pound or heavier asphalt roll roofing, lay on the floor and up the walls approximately 6".

D. Encapsulated Batts
Poly facings that are "nonperforated" act as a vapor retarder and should be considered interchangeable with other faced batts. A perforated poly "backer" film on one or both sides of the batt should be considered interchangeable with unfaced batts; i.e., a non-vapor retarder.

E. Spray Foam Insulation
Check with manufacturers for recommendations regarding the installation of a vapor retarder with spray foam applications. The perm ratings of closed-cell polyurethane and spray foam products vary from 0.8 to 2.5. Therefore, some do qualify as a vapor retarder in general construction situations. Open-cell spray foam perm ratings vary from 16 to 25 perms or more and do not technically qualify as a vapor retarder. For those spray foam products not qualifying as a vapor retarder, the use of foil-backed gypsum board or a vapor retarder paint applied to the interior wall surface is generally recommended.

In all cases, consult with the project architect, engineer, or building code official prior to the use of vapor retarders. ICAA Technical Bulletins are provided as a convenience for informational purposes only. ICAA and/or its members are not responsible for loss or damage caused by errors or omissions or any other cause.

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