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  1. #1

    Exclamation thumbs up or down on vapor barrier

    i am having a new home built in northwest ohio. i have collected a couple of quotes from general contractors to finish our basement. both quotes call for a vapor barrier (visquine?) between the new 2x4 wood studed walls and the existing concrete walls. i recently spoke with a fella who finished his basement and included a vapor barrier. this fella is confident, the condensation problem he has experienced is due to the vapor barrier. of course this news caused me concern. i am looking for direction. i plan on speaking with my contractor who i awarded the bid to very soon, definately before he begins his work.

  2. #2
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    Default Re: thumbs up or down on vapor barrier

    Vapor barrier ? .... yes and no.

    Around here it's mandatory the basement walls are insulated from top to bottom and covered with an approved vapor barrier ( 6mil poly or other ) for all new homes.

    The basement is considered conditioned space , especially if you plan on finishing it for a living area.

    However .... the complication is because it's a new constructed home with new building materials ...... lumber , drywall mud , paint and concrete.There are gallons of moisture that will evacuate from the material into the air which results in very high relative humidity ( RH ) inside the home for quite some time until the materials dry out.
    If your basement walls are poured concrete there will a large amount of moisture being evacuated as the concrete cures which happens for sometime after it's poured.

    If the basement walls are covered over immediately with a vapor barrier this will trap that moisture from the 2x4 lumber and the concrete, inside the wall cavity.
    It's not uncommon to see water on the inside of the vapor barrier soaking the insulation and creating mold on the lumber.

    You might consider holding off on finishing the basement until the RH level stabilizes which could take up to a year.

    When you do move into the home it wouldn't hurt to purchase a dehumidifier to help with the reducing the RH , or some type of mechanical ventilation as well opening the basement windows in warmer temps.

    Once the RH in the basement has stabilized then proceed with applying the vapor barrier over the insulation and finish as desired.

    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
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    Default Re: thumbs up or down on vapor barrier

    The problem with vapor barriers is that they are usually installed incorrectly.

    As canuk pointed, there is a condensation problem. The vapor barrier should keep water from seeping through and soaking the insulation, studs and drywall.

    However it does not stop the water from seeping through the porous concrete , and depending on where you live, on how new is the home and how humid are the weather conditions, that seepage can be pretty heavy and condense behind the VB.

    If you do not give this water a way out, it will eventually drip down and find its way into your basement, insulation and wall finishes.

    A vapor barrier should be installed in conjunction with some kind of drainage system that will collect the water behind it, and divert it to a sump pump that will the proceed to pump out and away from the foundation walls.

    The amount of moisture will determine the kind of drainage you need. Sometimes a baseboard system will suffice, but the best way would be to install a drain tile around the internal perimeter of the basement. This way you will be also relieving some of the hydrostatic pressure that is causing the water to seep through in the first place.

    There is no point in installing a VB if you are not providing drainage for the water collected between the VB and the concrete wall.

    It is also not a good idea to finish a basement without a vapor barrier, if you are using conventional materials such as drywall and the types of insulation you use above grade, because without it they will soak up that moisture that seeps trough the concrete. Wet insulation loses its R-Value and typical drywall will eventually grow mold and rot.

  4. #4

    Default Re: thumbs up or down on vapor barrier

    I would add to these posts that once you've allowed time for things to stabalize, check to make sure that moisture isn't still intruding. You may not see liquid water, but moisture in the form of humidity can create micro-environments on the surface of materials that encourage amplification of microorganisms (bacteria, molds, and some parasites). I've seen homes finished with various vapor barrier type systems that cover a concrete or brick wall that are not irrigated correctly (both inside and outside) to prevent wall cavity moisture problems and building deterioration. Whatever you do make sure that moisture incursion is controlled, not just covered up.
    Jason Yost, CIEC, CMRS, WRT
    Council-certified Indoor Environmental Consultant
    Council-certified Microbial Remediation Supervisor
    Water-damage Restoration Technician

  5. #5
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    Default Re: thumbs up or down on vapor barrier

    Dear Jasony,

    Our house is about 6 1/2 yrs old with a full basement which is cinder-block construction (approx. 30'x30'x8'high). The floor is a poured concrete slab and all of the basement walls are still bare block walls.
    These walls have never had any water leaks, i.e. water has never bled through from the outside. I want to finish this basement and my thought is to first use an acidic etching solution to remove all loose particles from the block walls, basically clean the blocks, patch any settling cracks, let dry, then use either DRYLOK or Behr's waterproofing paint (I used this method for my shop which is mostly underground as well).
    After the waterproofing paint dries, my plan is to stud out the walls with wooden 2x4's, insulate between the studs with R-13 with vapor barrier, and this vapor barrier paper will be facing the dry wall, then hang dry wall and finish.
    Does my approach seem like I am taking proper precautions in order to continue to have a dry mold-free basement?
    The company who installed the Radon exhaust system already sealed the gaps around the perimeter of the basement where the slab floor meets the block walls with a good caulk.
    Someone mentioned to me that instead of etching and water proof paint, that placing a plastic vapor barrier against the block wall, leaving the top and bottom of the plastic open will suffice as a vapor barrier. I'm not convinced though...What do you think or is there a sort of a thought process that I should consider??
    Thank you very much in advance for any help.
    toms
    from PA.

  6. #6
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    Default Re: thumbs up or down on vapor barrier

    Quote Originally Posted by toms View Post
    Dear Jasony,

    Our house is about 6 1/2 yrs old with a full basement which is cinder-block construction (approx. 30'x30'x8'high). The floor is a poured concrete slab and all of the basement walls are still bare block walls.
    These walls have never had any water leaks, i.e. water has never bled through from the outside. I want to finish this basement and my thought is to first use an acidic etching solution to remove all loose particles from the block walls, basically clean the blocks, patch any settling cracks, let dry, then use either DRYLOK or Behr's waterproofing paint (I used this method for my shop which is mostly underground as well).
    After the waterproofing paint dries, my plan is to stud out the walls with wooden 2x4's, insulate between the studs with R-13 with vapor barrier, and this vapor barrier paper will be facing the dry wall, then hang dry wall and finish.
    Does my approach seem like I am taking proper precautions in order to continue to have a dry mold-free basement?
    The company who installed the Radon exhaust system already sealed the gaps around the perimeter of the basement where the slab floor meets the block walls with a good caulk..
    The one thing I see with your proposed method ......... the DryLok or similar would be considered a vapor barrier since it seals the concrete block along with installing your insulation with a vapor barrier toward the warm side can be problematic. You are having a vapor barrier on both sides of the insulation which is not good and will trap any moisture that will get in the wall.

    If you feel the need to use the paint on sealer to the block walls only apply it on the walls to the grade level. This will allow the block walls to breathe out any moisture that maybe trapped.



    Someone mentioned to me that instead of etching and water proof paint, that placing a plastic vapor barrier against the block wall, leaving the top and bottom of the plastic open will suffice as a vapor barrier. I'm not convinced though...What do you think or is there a sort of a thought process that I should consider??
    Thank you very much in advance for any help.
    toms
    from PA
    This is an incorrect thing to do.

    The vapor concern is from the warm moisture laden air within the basement during the cold season. You want to prevent this moisture from entering the wall cavity in the first place.

    You don't want to have a vapor barrier on the cold side of the insulation .... which is the foundation wall.
    When moisture enters the walls it will pass through the fiberglass batts and contact the cold plastic and condense and be trapped .... causing mold issues.

    Besides ....cutting the bottom and top portions of the plastic defeats the intended purpose.


    Just some thoughts.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  7. #7
    Join Date
    Jan 2009
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    Default Re: thumbs up or down on vapor barrier

    Thank you canuk...can't tell you how much this has helped!!There's one thing that I just learned after posting my original question though.
    The outside walls which are under grade have been sealed with a industry standard tar-like sealer. The builder placed blue foam insulation after applying the tar sealer. So there's block wall, tar-sealer, blue foam insulation then the ground (I believe this blue foam is common in our area). Does this new information change your thoughts??
    Thank you again!
    Back to your reply to me...
    So in sticking with your recommendations, I probably shouldn't need the paint on sealer then?? Btw, the one wall which is completely under ground is under a concrete slab front porch. Guess I should've mentioned that ealier...
    toms

  8. #8
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    Default Re: thumbs up or down on vapor barrier

    toms ... the method described for the exterior of the foundation is a good method.
    The tar-like application is the damp proof material and the foam board actually does two things ....

    1- the foam acts as an isolation barrier to prevent hydrostatic pressure..... a good thing.
    The moisture contained in the soil can be forced into unprotected foundations from the pressure exerted by the surrounding soil ... known as hydrostatic pressure.

    2 - insulation from the exterior is very good method for foundations. This provides the thermal break at the source ..... which is advantageous.

    If you decide to add 1 inch rigid foam on the interior wall you will have very warm and better insulated walls.... which will greatly reduce or eliminate any chance for condensation issues.

    Hope this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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