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Community and Q&A

I want a encapsulated crawl without heating it?

SouthDakotaRoof | Posted in Energy Efficiency and Durability on

I have a small cinderblock crawlspace that shares a wall with my basement. I measured 8 foot by 12 (from the outside while in the yard) I bought this house recently so I dont know much about it. It’s totally dry, it has no plumbing or ductwork in it with a dirt floor. Just some electrical cords running into the house. I have paperwork showing that the previous owners had the crawlspace being encapsulated a part of their requirements when they first bought the house 10 years ago. So I can safely say the crawl has been ‘half encapsulated’  for 10 years without issue. By half encapsulated,  i mean it’s a terrible & unfinished job. The one vent it had was closed and covered with foam board.  It the 3 outer walls have foam board wedged to stand against them. The plastic sheeting all fell off as duct tape was used. Rimjoists unsealed & stuffed with fiberglass.  I have fixed the rim joists with caulk, foamboard & greatstuff. I’m working a wall at a time to check for cracks, hang 6 mill plastic sheeting, then foamboard sealed. Thing is, there is no mold or water issues so why should I bother heating it? What am I over looking? The exterior door is rotted cabinet looking trash so I suppose it’s technically been a vented crawl all along between that goofy door and the unsealed rim joists. Can I avoid the expense of running duct or the other option of a exhaust fan set in a rimjoist? Oh sorry this is in the black hills of south dakota. Climate zone 6

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  1. Expert Member


    You are in the enviable position of being able to do the work you want and then observe whether you have moisture problems going forward. Once you have fully encapsulated it (including a vapour-barrier on the floor), I'd suggest getting a humidity reader and see what happens. If you do find the RH is too high you have a few options.
    - Condition it by opening the space to your adjoining basement or the floor above with vents.
    - Do as above but mechanically exhaust the air to the outside.
    - Use a dehumidifier.

  2. CMObuilds | | #2

    Ironically that’s what my company was doing today. Encapsulating unconditioned crawlspaces in a condo development. We are in zone 6, I did one last year and it did nothing but lower existing humidity. Absolutely zero issues, no need for active heat BUT the floor is insulated for comfort.

  3. burninate | | #3

    Are the floors above this crawlspace well-insulated and well-airsealed?

    1. SouthDakotaRoof | | #4

      The floor above is not air sealed or insulated. I see signs that it used to have FG batts.

  4. Deleted | | #5


  5. brad_rh | | #6

    As part of this work, you should strongly consider a radon test. If you need to mitigate, do it now before putting a vapor barrier down.

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