Insulating stud wall crawlspace with rigid foam
Apologies if this has been answered already, but I haven’t been able to find an answer here or elsewhere. There are lots of great articles on rigid foam over concrete, but apparently a stud-wall crawlspace is uncommon–I haven’t found any recommendations for that configuration.
I have a 4′ crawlspace that’s composed of a stud wall on top of a footer (or buried foundation–not sure which is the proper term). Inside the crawlspace, there is just an inch or two of exposed concrete; the rest of the 4′ is studs. Currently the stud bays are filled with paper faced fiberglass, circa mid-90s (as are the joist bays). I’d like to either replace or supplement the wall insulation with rigid foam board. Is that foolish?
This is near Leadville, CO, at 10,000 feet. Humidity is really not an issue here, especially not in the winter. I suspect that in a more humid location, placing foam over fiber on an crawlspace interior would be asking for a mold habitat in those cavities–here, I’m not sure. The crawlspace is un-vented, but has an exposed (and powder dry) dirt floor. Access is via a conditioned, attached garage.
If I do remove the fiberglass, should I cut the foam and fit it into the stud bays, or attach it directly over the studs like wallboard? It seems like it would be a lot easier to attach it like sheathing, and there wouldn’t be thermal bridging from exposed studs to crawlspace air.
I realize that spray foam is an option, but that’s a little more daunting as a DIY solution.
Thanks in advance for any suggestions or info!
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