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  1. #1
    Join Date
    Jan 2011
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    Question Yet another radon / insulation question

    Hello,

    After a brief search, I couldn't find anything that exactly matches our scenario, so here it goes:

    We own a 1920 farmhouse in southern New Hampshire with a fieldstone foundation under the original part of the house. The joists of our living room floor are a mere few inches off of dirt, supported by horizontal timbers with stones underneath of them. (Can you picture it?) This "crawlspace" is normally inaccessible by humans, but you can peer into it from an adjacent basement. We recently had a pipe burst in the living room and the floor has to be replaced, so we'll briefly have rare access to the foundation. I'd like to ask about two areas of concern: radon and insulation.

    For radon, I understand that I can put down a thick, 20 mil vapor barrier. I've found and can purchase a suitable material, but I'm wondering how to attach it to the 6 inches of fieldstone. Some sources recommend parging with some kind of mortar/filler product and then attaching "strapping" (wood strips) to the parged surface using some kind of adhesive. Then the barrier is stapled to the "strapping". I'm imagining that I'd have to additionally caulk between the barrier and the foundation to get a nice seal. To make matters worse, how do I work around the stones supporting the timbers? I have a bad feeling about this. Sadly, I don't have the means right now to hire a professional, though insurance is covering the floor. I know that a professional would be best. What's the best way to handle this situation?

    For insulation, I've heard conflicting opinions. The word is that fiberglass in the joists is inexpensive and cost effective. However, while it's not outright "wet" down there, it does get moist in the summer and I've read that fiberglass breeds mold under such conditions. What about foaming the exposed foundation? (after parging and vapor barrier installation?) I've also found professional grade foam available for purchase. Would radiant barrier on the bottom of the joists be worth my while in the absence of batts down there? I've read that it only works well when there's an air gap between the barrier and the floor.

    Again, you have no idea how much I'd love to hire the pros, but it's just not happening right now. Thanks in advance for helping to ease the stress.

    Kind regards,

    Jim

  2. #2
    Join Date
    Jun 2007
    Posts
    6

    Default Re: Yet another radon / insulation question

    Please remember that if you use a vapor barrier sealed to the foundation to prevent radon gas from entering your living space, you must provide a venting system to permit the gas to exit the "crawl space." We installed a pipe-and-fan system which has taken care of our radon problem.

  3. #3
    Join Date
    Feb 2011
    Posts
    11

    Default Re: Yet another radon / insulation question

    This website should answer all of your questions about your radon problem and explain how to encapsulate your crawlspace. http://crawlspaceinfo.com
    Last edited by Derek Engle; 02-16-2011 at 04:20 PM.

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

    Exclamation Re: Yet another radon / insulation question

    Quote Originally Posted by NH_Jim View Post
    Hello,

    After a brief search, I couldn't find anything that exactly matches our scenario, so here it goes:

    We own a 1920 farmhouse in southern New Hampshire with a fieldstone foundation under the original part of the house. The joists of our living room floor are a mere few inches off of dirt, supported by horizontal timbers with stones underneath of them. (Can you picture it?) This "crawlspace" is normally inaccessible by humans, but you can peer into it from an adjacent basement. We recently had a pipe burst in the living room and the floor has to be replaced, so we'll briefly have rare access to the foundation. I'd like to ask about two areas of concern: radon and insulation.

    For radon, I understand that I can put down a thick, 20 mil vapor barrier. I've found and can purchase a suitable material, but I'm wondering how to attach it to the 6 inches of fieldstone. Some sources recommend parging with some kind of mortar/filler product and then attaching "strapping" (wood strips) to the parged surface using some kind of adhesive. Then the barrier is stapled to the "strapping". I'm imagining that I'd have to additionally caulk between the barrier and the foundation to get a nice seal. To make matters worse, how do I work around the stones supporting the timbers? I have a bad feeling about this. Sadly, I don't have the means right now to hire a professional, though insurance is covering the floor. I know that a professional would be best. What's the best way to handle this situation?

    For insulation, I've heard conflicting opinions. The word is that fiberglass in the joists is inexpensive and cost effective. However, while it's not outright "wet" down there, it does get moist in the summer and I've read that fiberglass breeds mold under such conditions. What about foaming the exposed foundation? (after parging and vapor barrier installation?) I've also found professional grade foam available for purchase. Would radiant barrier on the bottom of the joists be worth my while in the absence of batts down there? I've read that it only works well when there's an air gap between the barrier and the floor.

    Again, you have no idea how much I'd love to hire the pros, but it's just not happening right now. Thanks in advance for helping to ease the stress.

    Kind regards,

    Jim
    The first question to ask --- have you had a test done to see if you indeed have a problem with Radon?
    Radon is more of a concern in homes with basements that are directly coupled to the rest of the home. If the living space doesn't have regular air exchange then a buildup of radon gas as well as other contaminants can be an issue for indoor air quality.
    Usually crawl spaces are not directly coupled to the living space. Unless there are seveal leaking points of entry then Radon shouldn't normally be a concern --- if there are leaks from the crawl space then you have other issues like heat loss and moisture issues. Radon in a crawl space could be controlled with simple air exchange with vents.
    Also , laying plastic down on the dirt floor of the crawl space will also keep moisture issues down but will help with limiting any Radon gas. You could use foam in a can to adhere the plastic to the foundation wall --- you just need a thin bead because it will expand.

    Yes , insulating the perimeter walls of the crawl space will go a long way to help keeping the temperature inside the crawl space more regulated --- helping to keep your floors warmer. Combined with insulating the underside of the floors will greatly increase your comfort.

    Fiberglass is not an organic material --- mould lives on organic material.

    Ideally, if you could attach rigid foam boards to the underside of the floor joists and fill in the joist bays with batt insulation would be a great way to insulate.
    If you can't attach the rigid foam ensure you install something to hold the batts in place , otherwise they will sag and fall out.There are wire retainers available that are wedged in between the joists , wire coat hangers repurposed for this also works. Cut them in 16 inch lengths --- these will be longer than the space between joists ---- place them diagonally in between the joists to wdge them in place. The more the better to help holding the batts in place.

    I don't believe a radiant barrier would be of much use in this case. There isn't much radiant heat concern here.

    2 cents worth.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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