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  1. #1
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    Aug 2008
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    Default Insulating over a crawl space without access

    Problem: I have a 2200 sf house that has really limited space in the crawl space under the house. Access from below (for me) is not an option. The floors are not insulated (some of the walls are not insulated either). What is the best - most cost effective - way to get some insulation installed under the floors?

    Could you spray foam from the top through the floors? Would it stick the the floor joist?

    Rip up the sub-floors and install fiberglass bats from above?

    Would 1" of Expanded Polystyrene with another layer of OSB on top of the sub-floor provide enough insulation?

    Or find a really skinny non claustrophobic installer and hope he does a good job, because there are areas (~12") that I might be able to get into, but probably not out of, and I would never be able to inspect his work.

    Thoughts?

  2. #2
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    Nov 2007
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    Default Re: Insulating over a crawl space without access

    Quote Originally Posted by slawson2000 View Post
    Problem: I have a 2200 sf house that has really limited space in the crawl space under the house. Access from below (for me) is not an option. The floors are not insulated (some of the walls are not insulated either). What is the best - most cost effective - way to get some insulation installed under the floors?

    Could you spray foam from the top through the floors? Would it stick the the floor joist?

    Rip up the sub-floors and install fiberglass bats from above?

    Would 1" of Expanded Polystyrene with another layer of OSB on top of the sub-floor provide enough insulation?

    Or find a really skinny non claustrophobic installer and hope he does a good job, because there are areas (~12") that I might be able to get into, but probably not out of, and I would never be able to inspect his work.

    Thoughts?

    I don't know where you are at or what the practice is in your area but around here they put up skirting around the home and insulate the skirting putting in just a few vents in the ends to keep moisture down.

  3. #3
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    Default Re: Insulating over a crawl space without access

    Could you spray foam from the top through the floors? Would it stick the the floor joist?
    The foam would need some sort of backing to allow it to fill the cavity instead of just falling down into the crawl space.


    Rip up the sub-floors and install fiberglass bats from above?
    Either batt insulation or foam ... unfortunately an envasive method and wouldn't be cheap replacing the flooring..... but it may be your option if you can't get underneath.

    Would 1" of Expanded Polystyrene with another layer of OSB on top of the sub-floor provide enough insulation?
    would work ... although you would be raising the floor height which requires a lot of rework to all the baseboards and door trims and the doors themselves .... it would be better to rip up the existing floor than do this method.... in my opinion.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  4. #4
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    Default Re: Insulating over a crawl space without access

    Interesting, two different views from different parts of the country - Thanks.

    The house is skirted. Actually there is a stem wall at the perimeter with a small cripple wall up to the floor joist. Currently it is uninsulated and had a large number of vents to the crawlspace.

    I thought of insulating the walls of the crawl space and putting down a vapor barrier, closing off the vents and making it conditioned space (a really short basement). but I can not figure how to get a good vapor barrier down give the amount of working room.

    Reworking the trim is not that big of deal, because it is all getting replaced. It just seems that pulling up all the sub floor will be problematic.

    Foam - is there a reverse spray tip? Something like they use to rustproof cars? I was thinking that the foam should stick if it could be sprayed in the right direction, it does stick to ceilings doesn't it?

  5. #5
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    Default Re: Insulating over a crawl space without access

    Anyone have any more comments?

  6. #6
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    Default Re: Insulating over a crawl space without access

    Quote Originally Posted by slawson2000 View Post
    Anyone have any more comments?
    I'm assuming your crawl space is over dirt. Less than 12" is certainly not accessible to work. Is there plumbing under there that could freeze? I've had to walk away from a few jobs like that, because it was not cost effective to do anything. I would go with a perimeter insulation, but you will need to get a vapor barrier down somehow, especially if it is over dirt. Even if you tear up the floors and insulate from above, you would still have a moisture problem that would destroy your insulation work rather quickly. It will destroy your existing floor and create mold problems without a vapor barrier, insulated or not. Ventilating might remove some of the moisture (not all) and only make the floor colder. The best solution, although I'm sure you don't want to hear this, may be excavation to get enough room to do the job properly. Unfortunately, there is no easy way to approach your situation and solve all the problems.

  7. #7
    Join Date
    Nov 2008
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    Default Re: Insulating over a crawl space without access

    I had the same problem...about a 100 sqft area, three sides of the room faced the exterior.

    I was not willing to rip up the existing flooring. There was a pipe under the space, but it was for a steam radiator (could not get access either).

    Our solution was to install perimeter insulation. Insulate all the exterior walls and run the insulation (foam) down as far as possible. For the most part, this improved things. Not like the rest of the house...but significantly better than before.

    Best of luck.

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