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Insulating Crawl Space Floor Deck with radiant?

user-6445625 | Posted in General Questions on

For a new house in Zone 6 with a crawl space, we will spray the interior walls of the crawl to code but are wondering how to handle insulation in the floor decking given that we will have radiant floor with Warmboard. We welcome input!


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  1. Expert Member
    DCcontrarian | | #1

    If you're insulating the perimeter of the crawlspace it's conditioned space, but you may not want to heat it as warm as the radiant floor would naturally; a layer of fiberglass batts will cut down on the heat transfer. In zone 6, if you've got plumbing in the crawl space it's going to need some heat to keep from freezing. Since it's conditioned space vapor drive shouldn't be a concern, but if you're using faced batts I'd put the facing against the heat because that's the way vapor drive is going to go.

    The batting is easy to adjust after the house is built and occupied. I'd shoot for a crawl space temperature around 50F on the coldest days.

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