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Hi Kieran,
What type of foundation (concrete, stone) do you have? And how deep is the crawlspace?
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I asked because i feel like there’s something I’m missing. I can understand why they may want to spray foam the fieldstone foundation, but I don’t quite understand the logic behind spraying both the floor and underside of the subfloor (crawlspace ceiling).
My understanding of things could be wrong, but I would assume that Heatlok on the walls (and rim joist) to a thickness commensurate with your climate zone along with a vapor barrier on the floor with taped seams would be sufficient. The floor foam would be optional, but not necessary I believe. Then, some sort of conditioning strategy as per the code (dehumification, exhaust + makeup air from the living space, or HVAC return/supply) and you’d be set. No need to spray the crawlspace ceiling.
Hopefully one of the more experienced members and confirm (or totally blow up) my assumptions.
Couple of things:
- Demilec Heatlok HFO uses Honeywell Solstice as its blowing agent, which has a GWP of 1 (https://sustainability.honeywell.com/content/dam/sustainability/en/documents/document-lists/marketing/SolsticeLba-EnergySealHqCcspfRoofInsulation-CaseStudy.pdf).
- You could consider AeroBarrier as a way to get air sealing, and eliminate/minimize use of spray foam: https://aeroseal.com/aerobarrier/dealer-locator/
Is AeroBarrier paired with open cell spray foam for cavity wall insulation @ exterior wall be overkill? climate zone 2
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So did you go with any of this? How did it turn out?
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Are both of the crawl spaces relatively dry?
Is there a discernable comfort issue in the house? (leaky, drafty, other)
I might be inclined to address those two issues, but beyond that, the work probably won't pay for itself. So another approach is to address organically as you do projects such as you mentioned for the attic. The fundamental problem is many workers just don't care much about quality, so you spend all this money and get a 1/3 job...so it does not do what you really intend.
Tell the Aerobarrier folks you will make your crawl spaces empty with no people or furniture, and you want a quote on sealing...
Your reasons for staying away from spray foam are good ones, don't give up that position.
It's unfortunate that you haven't found a good contractor yet that will do air sealing. I've seen it done effectively with caulk and foam boards, which you can get low-VOC versions of.
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