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ThinkSharp OP t1_j5wckvw wrote

Reply to comment by lovallo in Insulating crawl space with sub-grade walls, or spray insulate floors? by ThinkSharp

Thank you. I think I’m ASHRE zone 4. Central WV (not the mountains). Winters are not typically severe but can be single digits a few times and we recently had negatives (dry bulb) during this bomb cyclone.

So you recommend if I insulate, do it at the walls mainly because of the moisture issue?

I realize I didn’t answer your whole question. Typical temps in the crawl space during winter are probably 55-60. Long t shirt feels perfect, short sleeve if working. Humidity is typically high. We had to install a vapor barrier and sump pumps. It gets foundation run in from one side. Correcting the swale outside is on my list for things this summer but part of the issue is a cement slab that needs raised. May not be able to handle that. In other words I expect it to always have some water coming in when rainy/snowy. I plan to NOT cover over the boards in that area to let them keep breathing and I intend to place a dehumidifier in that area of highest humidity/source.

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Traveling_Carpenter t1_j5wngkr wrote

You have a couple prescriptive options available in the model code if you go the path of insulating the walls, which is a good choice. Look at R408.3 in the International Residential Code - it spells it out pretty clearly. For a more plain-language perspective explanation, I’d check out the Fine Homebuilding article “crawlspaces that work.” Code available here: https://codes.iccsafe.org/content/IRC2021P1/chapter-4-foundations

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ThinkSharp OP t1_j5yc4jq wrote

Thank you, I’ll read each. That’s helpful because I don’t know where this stuff is already studied and prescribed so this is super helpful. No sense recreating the wheel

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