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  1. #1
    Join Date
    Feb 2008
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    7

    Default Frost on basement walls

    Hi, we have a new home with an unfinished basement since we dont use the space we dont heat it, We have noticed frost in the corners about a foot down, and also frost behind the insulation at the rim joist.We have removed all the insulation to let the area dry out. My question is do we have to have heat in the basement to prevent this problem?

  2. #2
    Join Date
    Aug 2007
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    1,131

    Default Re: Frost on basement walls

    Debbie,

    If this is indeed a new home (less than a year or so old) then it's still retaining alot of moisture which will need more time to dissipate.

    New concrete has ALOT of water in it and so does most construction lumber as it arrives on site.

    It would probably be best if you could ventilate this basement for a while (couple months) once the weather turns warm outside. However, this will only work during periods when the RH outside is low-ish. Once the outdoor RH rises to the hot & humid range.....you could actually be introducing more water vapor than you are dissipating. That moisture will then start condensing on the cooler walls and materials in the basement. So...ventilating to dry the place out......is dependant upon your locale and the weather conditions.

    Running a dehumidifier down there is also an option, but you'll have to warm things up a bit before that will be optimally effective.

  3. #3
    Join Date
    Feb 2008
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    7

    Default Re: Frost on basement walls

    My question was about winter months, will it be necessary to heat the basement in winter, I am sure it will cost a lot to keep heat on in an uninsulated basement for the winter,

  4. #4
    Join Date
    Aug 2007
    Location
    The Great White North
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    Default Re: Frost on basement walls

    Debbie1949 .... This may also be related to your other issues with of humidity and condensation on your windows.

    To add to ****hiller's post ....

    Depending on where you live ….. It is not a good idea to leave a basement completely cold, as this subjects the basement walls to freezing….. there is more heat lost on the top of the basement than on the bottom. That’s why you see the frost higher up the wall … which would be above the ground level outside.
    It’s likely the basement has just as much moisture in it as the rest of the house, perhaps more ….because moisture tends to migrate from warm to cold areas it’s collecting at the coldest areas and freezing.


    The perimeter rim joist are commonly insulated with fiber glass bats jammed up into the cavity….. the area should have been well sealed with caulking first. When the framing is placed onto the concrete foundation gaps can occur between this framing and the irregular surface of the top of the foundation. This will allow air infiltration if not properly sealed….. simply adding fiber glass bat insulation won’t stop air leakage.

    The batts should be covered with an acceptable vapour barrier and well sealed. or, for a super job, a well-fitted piece of Styrofoam, caulked all around could be used instead.
    If the existing insulation is simply opened to the area it is actually trapping the moisture from condensation and freezing.

    Reducing the humidity along with increasing air circulation in the basement area will help reduce this problem .

    Warming the air temperature along with reducing the humidity in the basement will help .

    Properly sealing and insulating combined with a proper vapour barrier …. the entire basement walls will make a big difference likely without the need to fully heat the basement.

    Hope this helps.

  5. #5
    Join Date
    Feb 2008
    Posts
    7

    Default Re: Frost on basement walls

    Hi, We have removed all the insulation from the rim joists, to find the wall on the north side and east side of the basement had condensation and frost.Rest of the walls were dry under the insulation. We have removed the wet insulation to allow the walls to dry. Would there be a problem with not putting any insulation back up there?

  6. #6
    Join Date
    Aug 2007
    Location
    The Great White North
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    4,045

    Default Re: Frost on basement walls

    Leaving the insulation removed temporarly while things dry shouldn't be an issue.

    If your asking to leave it out permanently .... well that defeats the intended purpose of preventing heat loss/cold penetration in those areas.... especially on the North side.

    For example.... here for the last few days with a howling wind (30mph) the temperature is down to 52 below ... I would certainly would want insulation around the rim joist areas otherwise the floors would be ice cold.


    Just my thoughts.

  7. #7
    Join Date
    Feb 2008
    Posts
    7

    Default Re: Frost on basement walls

    So I guess there is no way getting around not having to have heat on in the basement in winter months. Its a big area to have to heat,especially with the walls not being insulated.

  8. #8
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Frost on basement walls

    Or........ insulate all the walls top to bottom and completely cover with a sealed vapor barrier ..... would be cheaper than having to heat the uninsulated basement.

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