Vapor Retarder

Function & Code Requirements

Vapor retarders minimize the movement of moisture from the interior of the building into the cavity wall where condensation can degrade insulation and structural members. As per R318.1 2006 IRC (International Residential Code), “In all framed walls, floors and roof ceilings comprising elements of the building thermal envelope, a vapor retarder shall be installed on the warm-in-winter side of the insulation.

Exceptions:

1. In construction where moisture or freezing will not damage the materials.
2. Where the framed cavity or space is ventilated to allow moisture to escape.
3. In counties identified as in climate zones 1 through 4 in Table N1101.2.” Vapor retarders, while required by the 2003 International Building Code, are not mentioned in the 2006 International Building Code.

Continuous vapor barriers to reduce the passage of water vapor into the wall generally are used only when insulation is placed on the inside face of the wall. The relatively small amount of moisture that does get into the wall from the inside of the building will diffuse provided that the exterior surface is “breathable.”

• Air Barriers, Vapor Retarders and Weather-resistive Barriers: Are They All the Same?
• Condensation - Prevention and Control
• Condensation Control in Concrete Masonry Buildings
• Design for Dry Single-Wythe Concrete Masonry Walls

Companies Offering Vapor Barriers, Liquid-Applied

Company	City	State
Hohmann and Barnard, Inc.	Hauppauge	NY
Crown Masonry & Construction Materials, LLC	Kansas City	KS
Ernest Maier, Inc.	Bladensburg	MD
MASONPRO, Inc.	Northville	MI
Thompson Building Materials, Inc.	San Diego	CA
Waldo Bros. Company	Boston	MA