Insulation and Vapor Retarder for Basement / Crawlspace Combination
Hey everyone thanks for your time
I live in climate zone 5. I’ve got a 100 year old home with a not directly conditioned (mechanicals are in the basement but no registers for heating or cooling) full height basement, unfinished. Concrete block foundation. There’s a partial depth crawlspace (about 3 foot from dirt floor to floor joists for 1st floor) that openly communicates air with the basement. No access door.
I’m getting a radon system put in but wanted to be sure of the envelope details before they encapsulate. I was going to use rigid foam board for the crawlspace walls. This should be behind the vapor barrier, correct? And given the floor is just a couple feet below ground surface and while I have access, should I also insulate the dirt floor of the crawlspace before they encapsulate? I could use rigid insulation there also as I can’t think of another easy and relatively cheap method.
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This article, Sealing a Crawlspace, has answers and details pertinent to your questions. One thing I know all the experts here will advise is to do a comprehensive assessment of both spaces to ensure there are no bulk water or moisture issues before doing anything to seal and insulate.
Absolutely understood and did go through that process. I just wanted one more quick affirmation by some people to make sure it all seemed appropriate. And I’ve had some people tell me the dirt floor didn’t need insulation but to me since it isn’t super deep it would benefit. especially as people sub slab insulate and it’s even deeper.