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Vapor Barriers

5 Essential Steps to Getting Real Results

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Vapor Barriers can seem confusing, but there's a simple rule on how to use them in your home:

Vapor barriers go on the warm side.

What makes it challenging, is that for most homes in America, there's a winter and a summer. Because climate zones vary along with almost endless variations in building construction, check with your local code officials to see what you need in your area when using 2lb closed cell spray foam.

Foam It Green, like all 2 # closed cell spray foams, is a Class III vapor retarder. If your local building code requires a class II vapor barrier or lower, that means you'll need a vapor barrier in addition to your foam. Each code lists off various items that qualify for your area. The two most common are kraft paper and poly plastic sheeting.

If you're doing a hybrid wall using Foam It Green in conjunction with fiberglass batt, first, spray in the foam. Then, if you need a vapor barrier on the inside, install the batt with the paper facing you. Make sure to first do a minimum of 1/2 the total R-value in the closed cell foam. (For more information about condensation midpoints, refer to our 2x4 or 2x6 wall videos.)