Crawl spaces, what side of the wall does the insulation go on?

Discussion in 'Homesteading Questions' started by canfossi, Jul 9, 2006.

  1. canfossi

    canfossi Well-Known Member

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    The foundation company put in a crawl space for me and I was wondering what side the rigid insulation goes on? It's a vented crawl space and the subfloor will be going on in a week or so. They tared the outside and then parged it, so I'm assuming the insulation goes on the inside? What about the vapor barrier? Correct me if I'm wrong. The crawl space floor is concrete. We get cold winters, -20C at night and there will be only the septic pipes in the crawl space. All the other pipes will be above the subfloor. Just want to know before any backfilling is done. Thanks Chris
     
  2. scaryguyoy

    scaryguyoy Well-Known Member

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    Check the U.S. dept of energy website they have all kinds of insulation information.I think you can insulate both sides,depending on what you want to spend.
    scary
     

  3. susieM

    susieM Well-Known Member

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    Well...I was going to say that it all depended on how comfortable you wanted the whacko guy, that lives under there, to be.
     
  4. RedneckPete

    RedneckPete Well-Known Member

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    On the inside. In Ontario it's R20 or 2 1/2 " of SM, which must extend to 2' below outside grade. Use two layers, one 1" and one 1 1/2" thick. Overlap the joints and use ship lap edged SM, then tape the inside seams with tuck tape. No need for vapour barrier.

    Pete
     
  5. mpillow

    mpillow Well-Known Member Supporter

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    Our board insulation is on the outside of crawl space....floors are insulated from inside the crawl space....if you live in a cold area like we do (Maine) a heat tape is a wonderful thing to use if there is any chance of pipes freezing underneath...we plug ours in around Christmas and unplug end of March..
     
  6. littlebitfarm

    littlebitfarm Scotties rule! Supporter

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    If you really want it tight wait until the decking is on and then have use the spray foam. It will seal it tight!

    My crawl space in central Illinois was always damp. But then it is real humid outside in the summer. I shut the vents and had them spray insulation all around and the first foot or so of floor space. Put a dehumidifer in there, runs a couple hours a day in the summer, couple hours a day in the winter. Crawl space is much drier than it ever was!

    Kathie
     
  7. canfossi

    canfossi Well-Known Member

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  8. ttryin

    ttryin Well-Known Member

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    Try Buildingscience.com/sitemap.htm

    More work for you, I know, but there are many details to putting together a workable picture. At the above website there's a great pdf on "conditioned crawlspaces" -- which you might look into instead of a vented crawlspace. I have one done as a conditioned crawlspace and was amazed at how dry it was and how little damp came though to the first floor. I didn't open it up for two years. This year, I have it open on a couple of warm dry days.

    Good luck.

    P.S. If I was ever putting in a concrete floor, I'd read read read about putting plastic and/or hard insulation under the concrete. Concrete absorbs a lot of moisture.

    T
     
  9. agmantoo

    agmantoo agmantoo Supporter

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    Here in the humid South to combat moisture the building code requires a continuous heavy mil poly vapor barrier over the entire crawl space. This is without concrete, just over the dirt. I was told recently that the vents were soon to be eliminated from the underpenning. Seems the house stays drier without the vents. This info came from a county inspector.
     
  10. SolarGary

    SolarGary Well-Known Member

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    Hi,

    If you are going to have a vented crawl space, then you want to insulate the floor above the crawl space, not the walls. If you insulate the walls, and have vents, the vents just allow cold air to get around the insulation.

    A lot of people think that the better solution is to not use vents, and insulate the walls. That is, build it like you would a basement. If you had a dirt floor, you would want to put poly over it, and seal the seams and edges to keep the moisute level down.

    This is a very good writeup on the pros and cons of vented vs non vented -- and how to do each:
    http://www.builditsolar.com/Projects/Conservation/Insulation/CrawlSpace29238.pdf

    I converted mine from vented to non-vented with insulated walls and sealed floor -- it has worked fine, and (I think) saves energy.

    Gary
    www.BuildItSolar.com