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Spray foam info

Starting a new build (1 1/2 basement walkout), all 2x6 exterior walls w/ brick veneer in GA, CZ 3. Above grade, would like to do spray foam in 2x6 walls, 1/2" or 1" of rigid foam board on the exterior, and a 1" air gap. Will this require a housewrap or can I do without the rigid foam and go with a housewrap? Also, any recommendations about insulation strategies for the finished basement. Thanks!

Asked by David Myles
Posted Tue, 07/22/2014 - 15:29
Edited Tue, 07/22/2014 - 15:53

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David,
Q. "Will this require a housewrap or can I do without the rigid foam and go with a housewrap?"

A. Every wall needs a water-resistive barrier (WRB). A WRB is required by code, and is recommended by building scientists.

There are lots of different products that can be used as a WRB, including asphalt felt, plastic housewrap, and liquid-applied products. For a list of your options, see All About Water-Resistive Barriers.

It's possible to use rigid foam as a WRB, but there are a few caveats. It can be harder to integrate flashings with your WRB if you choose to use rigid foam as your WRB. For more information on the pluses and minuses of this approach, see Using Rigid Foam As a Water-Resistive Barrier.

It's possible to skip the rigid foam and to install housewrap without the rigid foam, but I don't recommend this approach for your house. Rigid foam provides an important function behind brick veneer: namely, it stops inward solar vapor drive, which can cause problems during the summer. Moreover, the rigid foam provides a useful thermal break to limit thermal bridging through your studs.

Q. "Any recommendations about insulation strategies for the finished basement?"

A. I suggest that you read this article: How to Insulate a Basement Wall.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/22/2014 - 15:48
Edited Tue, 07/22/2014 - 15:57.

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