Question for Worthy.

cheri127May 19, 2012

Hi Worthy. I have read and re-read Lstiburek's crawl space paper and I think I finally get it. Could you tell me if this is right? One can completely cover the wood joists with spray foam as long as one uses 3" high density foam? The reason the open pier approach works is because the crawl space isn't colder than the outside air?

If all this is true, would I be able to correct my flawed crawl space by

1) covering the floor with a 20 mil vapor barrier

2) remove batting then spray the wood with 3" of high denisty foam

3) continue to use SaniDry dehumidifier

I can't do the open pier approach because most of the crawl space is below grade.

I have read many of your posts recently they are so informative. Thanks for taking the time to share so much information.

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You overlooked two steps:

1) a drying mechanism--such as a supply of conditioned air from the interior and exhaust (See link--Figures 2, 3, 4)

2) insulation on the perimeter walls--spf or extruded polystyrene board (XPS)

The 20 mil barrier is overkill if you're not using the crawlspace.

Here is a link that might be useful: Conditioned Crawlspace Construction

    Bookmark   May 30, 2012 at 6:20PM
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If you're insulating the perimeter, forget insulating the ceiling.

    Bookmark   May 31, 2012 at 8:18PM
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