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Community and Q&A

Radon mitigation with sealed crawlspace and partial walkout basement

NormanWB | Posted in Mechanicals on

Does anyone know of a resource that addresses radon mitigation for a foundation area with a sealed crawlspace and partial walk-out basement on new construction in Zone 3A?

I am assuming the crawlspace and basement mitigation systems can share an exhaust pipe and I have a good understanding of the under slab portion for the basement. So, what is the best method for the crawlspace?

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  1. GBA Editor
    Martin Holladay | | #1

    The usual way of installing perforated pipe for a radon mitigation system in a crawl space is to install the pipe in a trench filled with crushed stone; the horizontal lengths of pipe are installed under 6 mil (or thicker) polyethylene. If the crawl space has a slab, the details are exactly like those required for a basement.

    The pipes under the crawl space polyethylene can be connected to the same riser used for your basement system. For more information, see this article: All About Radon.

    The illustration below (from the EPA) doesn't get the insulation details right on the crawl space (you want insulation on the crawl space walls, not in the joist bays above the crawl space), and shows that all of the perforated pipe is above the soil. That approach will work, too, although I think it's better to have a deep layer of crushed stone under the polyethylene, with the horizontal pipe in the stone layer.

    If you have any doubts about these details, you should consult a certified radon mitigation contractor.


  2. KeithH | | #2

    Does your crawlspace have a concrete slab or just dirt?

    This is a newly built home without a system? Is radon not a general problem in your area?

  3. NormanWB | | #3

    Keith: Dirt floor. Construction not started, yet. Radon is a possibility in my area per EPA map. We will install a passive system to start, then test.

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