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Community and Q&A

Vented crawl space

rstarrett | Posted in Green Building Techniques on

We’re building a pretty good green home in Gardnerville, NV, a place that gets 8″ rain per year. We get cold in the winter (-10°) and are pretty warm in summer, about 10 days with >100° temps. Radon is an issue in our area. Our new home is being constructed with SIPs, therefore no attic space. We have natural gas at the site, pretty cheap in Northern NV. Our plan is forced air heating via Natural Gas in winter and a few days in summer when we’ll use A/C.

We need a crawl space to route the HVAC ducts between the floor joists. Sealed crawl spaces seem to make sense in the southeast, but what do you suggest for our arid climate? I have seen ex cathedra comments: “… crawl spaces must be sealed.”

My builder wants to use traditional insulation bats between the floor joists with a vented crawl space, keeping the HVAC stuff and plumbing high up next to the floor. I suggested isolating the floor system with blown-in insulation.

What do your editors suggest for our western construction project?

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  1. GBA Editor
    Martin Holladay | | #1

    For a variety of reasons, a sealed crawl space makes sense.

    For one thing: if you get winter temperatures as low as -10 degrees, it's certainly possible that your pipes will freeze if you ventilate your crawl space.

    Second: it's going to be very hard to make sure that your ducts are inside of your home's conditioned space if you vent your crawl space.

    You will save energy and have fewer plumbing emergencies if you build a sealed crawl space. The details aren't that complicated. Here is a link to an article that explains what you need to know: Building an Unvented Crawl Space.

  2. rstarrett | | #2

    If I seal the crawl space with foam panels against the stem walls and vinyl on the ground, that will involve some expense. Would I then not insulate the subfloor, thus saving some money to use for the sealing process? Note that nobody is concerned about moisture here; this is high desert at 4600ft with a very dry climate and constantly low humidity.

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