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Encapsulated crawlspace

user-6919496 | Posted in General Questions on

We are considering encapsulating a Crawlspace for a 600 square foot single story house in North Carolina located very near the border of Climate Zone 3A and 4A. The home is currently heated by a wood stove and cooled with a window unit A/C. The attic has been air sealed and insulated.

Typically, we’d introduce conditioned air into the crawlspace via duct, but having none, should we install a small fan and exhaust through the foundation wall? We’re planning to airseal the house floor. Should we consider an air grill between the house and the crawl? I’m not a huge fan of this, however would respect your input.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    User-6919496,
    First of all, can you tell us your name? (I'm Martin.)

    Yes, the best approach is to install a properly sized exhaust fan in your rim joist, as well as a grille in your floor to provide makeup air from the conditioned space above. All the details you need are in this article: "Building an Unvented Crawl Space."

  2. user-6919496 | | #2

    Sorry, Martin. My name is Marty Blackwell. I dabble in Home performance and love the science of it all. I’m certified as a building analyst, but am currently teaching plumbing at a local community college. Thank you for your quick response.

  3. Stockwell | | #3

    Marty--this is also a good reference that was written right here in NC. As they explain in the study, another option is to totally seal the crawl and just dehumidify with no air exchange

    https://www.advancedenergy.org/portal/crawl_spaces/pdfs/Closed%20Crawl%20Spaces_An%20Introduction%20for%20the%20Southeast.pdf

  4. Jon_R | | #4

    Note that anything that depends on the HVAC system or the interior being conditioned won't work during mild weather when the interior isn't conditioned. You are likely to get some mold during those periods.

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