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  1. #1
    Join Date
    Jun 2007
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    81

    Default air coming through cinder block foundation wall

    Our basement has been mostly finished. The walls are cinder block and there are electrical outlets set into one wall; the wiring comes up from below through conduit. (How that works I don't know since the wall is sitting on the ground.) During cold weather cold air blows out through the outlets. I took the covers off and you can see the cobwebs etc blowing in the breeze. In the room above that wall you can feel cold air coming up through the floor boards right next to the wall. The house is 42 years old and it's a good bet the cells in the cinder blocks are not filled so the cold air, wherever it comes from, its probably just going right up through the blocks, around the top plate and right up through the floor.
    I'm trying to find out where the air comes from. The outlets are below grade. Walking around the house, there are no obvious points of entry for the air. Has anyone ever heard of this?
    Thanks

  2. #2
    Join Date
    Mar 2009
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    1,387

    Default Re: air coming through cinder block foundation wall

    Howdy the cinder block wall is chimney ing the air. Any crack or separation of grout allows this convection of heat an air currants. So at the top plate is the block open? If so you could fill the wall or cap the wall with foam insulation to stop the up flow of air. The spray foam cans that say they are ok with electrical can be used to seal the openings in the electrical boxes( spot plugging holes - not filling up the outlet with foam) and foam gasgets can then be installed under the outlet covers.

  3. #3
    Join Date
    Jun 2007
    Posts
    81

    Default Re: air coming through cinder block foundation wall

    Quote Originally Posted by Timothy Miller View Post
    Howdy the cinder block wall is chimney ing the air. Any crack or separation of grout allows this convection of heat an air currants.
    Between the two outlets, there's an awful lot of air flowing for it to be coming in through a crack. And the outlets are about 10 feet apart. I can see the air flowing up through the cells, but I can't get how it's getting in in the first place.
    So at the top plate is the block open?
    The basement ceiling in that room is finished so we can't see the tops of the blocks at that point.

    Thanks for the response.

  4. #4
    Join Date
    Mar 2008
    Location
    nova scotia, canada
    Posts
    1,522

    Default Re: air coming through cinder block foundation wall

    its sounds like convection air movement. it might not neccessarily mean that there is a draft.

    putting it simply warm air is escaping through the holes in the block which creates air movement which can simulate a draft

    do as mentioned earlier, pick up a few cans of spray foam and fill the voids. and on your next house avoid a block wall foundation. in my region block wall foundations are an absolute nightmare to work on
    fire up the saw and make some dust

  5. #5
    Join Date
    Jun 2007
    Posts
    81

    Default Re: air coming through cinder block foundation wall

    Quote Originally Posted by jkirk View Post
    its sounds like convection air movement. it might not neccessarily mean that there is a draft.

    putting it simply warm air is escaping through the holes in the block which creates air movement which can simulate a draft
    I'd like that to be true, but I'm talking about seriously cold air blowing out of the electrical outlets, not just moving air.
    In your scenario, where would the warm air be coming from?

  6. #6
    Join Date
    Mar 2008
    Location
    nova scotia, canada
    Posts
    1,522

    Default Re: air coming through cinder block foundation wall

    the warm air will be comimg from inside the house, warm air always moves from warm to cold


    other wise the cold air is coming through the joint between the floor system and the top of the foundatin wall
    fire up the saw and make some dust

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