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  1. #1
    Join Date
    Jan 2012
    Posts
    1

    Default Fieldstone basement w/ poly vapor barrier - how to insulate

    I have a fieldstone basement covered with 15mil poly that directs any water in to my french drain. This part of the system works well and has prevented any incoming water from finding its way on to the floor, but now I find myself in a strange situation where I really don't know what to do for insulation so that I can finish the basement. I have read that I don't want a double vapor barrier, but normally in Massachusetts it seems like you would want the vapor barrier on the warm side of the basement, but I no longer have that option.

    What are my options to avoid a future mold problem?

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Fieldstone basement w/ poly vapor barrier - how to insulate

    You have a tricky situation there.

    Whenever thinking about finishing a basement I recommend to ensure there aren't any issues with moisture and check the relative humidity ( RH ). Seems as tough you have addressed water control in the basement but , you need to ensure the RH doesn't get any higher than 40 - 50 % ---- the lower the better in reducing mold and milde issues.

    The insulaing will be difficult in part because of the vapour barrier on the cold surface also, because of the irregular surface of the wall.
    This might be a good candiate for spray foam insulation to be used here.
    It's possible in your particular region 1/2 pound open cell will be acceptable since it may allow any drying required to be be done to the interior.
    The 2 lb. closed cell foam may also be a good candiate.

    I've know of one foundation simialr to your's --- though the covering was a dimpled product --- and spray foam was used over the entire wall surface --- then the wall framing was placed in front and covered with moisture resistant drywall.

    You will definately need to check with your municipal building office as to their requirement and recommendation.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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