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  1. #1
    Join Date
    May 2003
    Location
    Farmington, New Mexico
    Posts
    6,571

    Default I have a question on insulating a floor

    My house is an early 60's model with hardwood flooring over a crawl space. There's a bit of batt insulation between the floor joists, but not much. My kids are all out of the house and the pets are on their last legs so we're planning to pull the carpet and refinish the wood floors, which are stunning.

    I think I can do this myself over a few weeks. I'll pull what's left of the old stuff off and use batts that can be stapled upside down. I don't think a moisture barrier is necessary here in the high desert.

    Wintertime temps regularly get down to zero or below, and the crawlspace is ventilated with several screened 6"x12" openings on the exterior walls.

    My question is how much R-value is reasonable in a crawl space?
    Nobody ruins my day without my permission, and I refuse to grant it...

  2. #2
    Join Date
    May 2011
    Location
    Algoma dr. Ontario, Canada
    Posts
    811

    Default Re: I have a question on insulating a floor

    Can't give any advice about R value for your climate; just a suggestion that if you do go with the stapled up batts, to strap underneath th with lath on close centers for support or the batts start to fall after a few years when the paper gets brittle. Have seen poultry netting used too. 1/4 plywood ripped into strips is a good way to get the lath.

    I itch something fierce from fiberlass and no stranger to crawlspaces.

  3. #3
    Join Date
    Jan 2011
    Location
    Athens, OH
    Posts
    2,681

    Default Re: I have a question on insulating a floor

    There's differing schools of thought on insulating floors above crawlspaces. Some say you are best off to insulate the walls of the crawlspace, others the floor. Here the recommendation is at least R19 but, generally we put as much in as the joist cavity will hold. Better yet, put sheathing on the underside of the joists and have loose insulation blown in.
    Politics is the entertainment branch of industry. -Frank Zappa

  4. #4
    Join Date
    Aug 2012
    Location
    Portland, Tennessee, USA
    Posts
    241

    Default Re: I have a question on insulating a floor

    Have to agree with Crofter about straps. A good & more R value option is spray insulation. I have read it delivers more bang for the buck as far as R value is concerned. cg3 has a good idea as well. Might pose a problem if you ever have a water leak. Or maybe not.
    Beeman
    All things may be lawful; but not all things are advantagous.

  5. #5
    Join Date
    Feb 2012
    Location
    West Bath, Maine, United States
    Posts
    1,137

    Default Re: I have a question on insulating a floor

    Agree. that strap across the joists breaks the conduction of the joists which have almost no R value.
    4 yrs, Peak 14, back to zip, T lite; godfather to brother's 3.

  6. #6
    Join Date
    Jun 2009
    Location
    Montgomery County, NY
    Posts
    1,717

    Default Re: I have a question on insulating a floor

    Barry cant you find some recycled 4 inch foam sheets around? I just insulated most of my garage with that stuff and it only cost me 65 bucks for the recycled foam boards. Maybe you could find an old walk in freezer and rip it apart. Aweful good insulation and fairly easy to install once I cut it to fit.

  7. #7
    Join Date
    Jan 2011
    Location
    Athens, OH
    Posts
    2,681

    Default Re: I have a question on insulating a floor

    That'a a good one, too. Anything beats messing with fiberglass batts in a crawlspace.
    Politics is the entertainment branch of industry. -Frank Zappa

  8. #8
    Join Date
    Jun 2007
    Location
    mineral county,Montana USA
    Posts
    805

    Default Re: I have a question on insulating a floor

    i like the blanket around the perimeter better than insulating the floor.

  9. #9
    Join Date
    Nov 2011
    Location
    Rader, Greene County, Tennessee, USA
    Posts
    6,093

    Default Re: I have a question on insulating a floor

    In my view, whether it is cost effective to add additional insulation to the underside of a floor should be evaluated in terms of the entire house.

    For instance, if the ceiling also has a [relatively] low R value in total insulation, then it may be a better plan to add more insulation to the ceiling instead of the floor. Spend your money and effort where you get the best overall return.


    This DOE insulation calculator offers advice based on location (first 3 digits of zipcode) for various house components:
    http://web.ornl.gov/~roofs/Zip/ZipHome.html

    .
    Last edited by Rader Sidetrack; 01-16-2014 at 06:31 AM. Reason: add link
    Graham
    USDA Zone 7A Elevation 1400 ft

  10. #10
    Join Date
    Dec 1999
    Location
    DuPage County, Illinois USA
    Posts
    9,421

    Default Re: I have a question on insulating a floor

    There you go Barry, construction is no different than beekeeping. You'll rarely get two of the same opinion.
    I've done it both ways, depending on the circumstances. I favor insulating the perimeter foundation. This way, none of the mechanics are covered up. Less pain and hassle for those that have to work in that space.
    Regards, Barry

  11. #11
    Join Date
    Dec 1999
    Location
    DuPage County, Illinois USA
    Posts
    9,421

    Default Re: I have a question on insulating a floor

    Quote Originally Posted by Rader Sidetrack View Post
    Spend your money and effort where you get the best overall return.
    If that's the case, buy airline tickets and go visit your grandkids!
    Regards, Barry

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