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Community and Q&A

Should we install a vapor barrier or no?

Carol Hepler | Posted in Energy Efficiency and Durability on

Our house was build in 1958 and a recent termite inspection led to a recommendation that we have a vapor barrier installed in our crawl space. We have never had one before (living in the house for 20 years) and it never seemed to be a problem. Do we need one?

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  1. GBA Editor
    Martin Holladay | | #1

    If your crawl space has a dirt floor, it definitely needs a vapor barrier installed on top of the dirt. This could be 6 mil polyethylene, or something more sturdy. Lap the poly at the seams, and seal the seams with a high-quality tape. Use bricks or rocks to hold the polyethylene in place.

    If your crawl space has a concrete slab, it still may benefit from a layer of poly, although installing one on top of a slab is rarely done.

    For more information on this issue, see Building an Unvented Crawl Space.

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