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Community and Q&A

Crawl Space and Insulation

William Wingett | Posted in Energy Efficiency and Durability on

My sister lives in Alabama in a house that is a couple hundred years old and it sits appox. four feet off the ground. The problem is – she has no insulation in her her floors and won’t put any in because she was told that she would have a mold problem.

I thought that plastic on the ground and attached to the walls would keep out the moisture. But someone has her that you must leave holes in the plastic to let the moisture escape. Isn’t that wrong? What’s the best way?

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  1. GBA Editor
    Martin Holladay | | #1

    Start by reading this article: Building an Unvented Crawl Space.

  2. GBA Editor
    Martin Holladay | | #2

    I forgot to write -- you're right, of course, that you don't want to poke any deliberate holes in the polyethylene vapor barrier installed on a crawl space floor.

  3. 5C8rvfuWev | | #3


    Martin left out the need for a thermal break at the band joist. Usually, with a termite strip the band joist is insulated with batt insulation.

    there is a great diagram by Advanced Energy (in North Carolina, so they focus on SE crawl spaces) in the links Martin provides to them in the left margin of resources with the blog at his link.

    Good luck.

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