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Thread: Vapor barrier

  1. #1
    Join Date
    Aug 2011
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    1

    Default Vapor barrier

    Im replacing my vapor barrier. I went to buy some plastic and the sales person told me that the preferred method is now to staple the plastic to the floor joists overhead in the crawl space. I could describe it as a thin plastic ceiling forming a barrier between the air in the crawl space and the house. I like the sound of this (have allergies) but cant find any info supporting or contradicting. Any input? Thanks

  2. #2
    Join Date
    Jul 2010
    Location
    SoCal
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    6,308

    Default Re: Vapor barrier

    It may be extremely difficult to apply, secure and install if your crawl space is tight. Plus, it will restrict access to your plumbing, without cutting and tearing.

    And if you suffer from allergies, don't even think of going in the crawl space.

  3. #3
    Join Date
    Nov 2011
    Location
    Charlotte, NC
    Posts
    12

    Default Re: Vapor barrier

    OMG! NO!
    vapor barrier on floor! some parts of the country you also need to insulate at the floor.
    placing the poly at the floor level will trap humidity in the joists, which will cool and condense right on the wood. You will most likely end up with major mold issues.
    Worst advice I've heard all day!
    Helping Homeowners understand the Typical Causes and Solutions to Hidden Content issues!

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,916

    Default Re: Vapor barrier

    The vapor barrier in colder climates goes right under the drywall. In warmer climates the vapor barrier goes right under the exterior siding. In either case, the vapor barrier is part of the insulation envelope.

    Where is your house?

  5. #5
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,774

    Default Re: Vapor barrier

    Quote Originally Posted by tomaquar View Post
    Im replacing my vapor barrier. I went to buy some plastic and the sales person told me that the preferred method is now to staple the plastic to the floor joists overhead in the crawl space. I could describe it as a thin plastic ceiling forming a barrier between the air in the crawl space and the house. I like the sound of this (have allergies) but cant find any info supporting or contradicting. Any input? Thanks
    Was this advice obtained from Homedepot by any chance?
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

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

    Default Re: Vapor barrier

    really though, eh jack gotta love those "experts" in the orange smocks......
    fire up the saw and make some dust

  7. #7
    Join Date
    Mar 2009
    Posts
    1,387

    Default Re: Vapor barrier

    Asume your currant plastic is on the dirt floor of the crawlspace. The best practices is to replace it with a 6 mill plastic and caulk to the foundation wall - but why remove the old lay new over it and avoid punctures from rocks in the soil below the old....
    A great time to consider insulation of the floor 20% of heat loss is threw floors. A best practices is to install it and then house wrap- it allows moisture vapor transfer .

    But never plastic to the floor joist as the joists need to be able to dry out as moisture levels change in the crawlspace. While your down there are the rim joists insulated great time to install 2" of foam caulked into place this is a huge improvement in keeping the home cozy
    Any an all of my comments are just my opinion and not to be confused with facts.

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