Insulating a vented crawlsapce
I’m helping a friend do some energy improvements. The house is from the 50’s and seems to be made of concrete block with stucco on the exterior and plaster on the interior. I don’t think there’s much or any insulation in the walls.
The crawlspace is vented, and the furnace is down there, so not an ideal situation. I think it would be worth encapsulating at some point in the future, but I think it’s too much work/cost to do this year.
The floors get cold in the winter, especially near outside walls. Would it be worthwhile to insulate the rim “joist” (it appears to be just a concrete block) while leaving the venting in place? That would provide some insulation between the rim “joist”, which is the coldest part of the crawlspace, and the perimeter of the floor. Obviously the crawlspace is cold because it’s vented, but it’s not as cold as outside because it gains heat from the ground, from the uninsulated floor above, and from the leaky heating ducts. So although insulating the rim joist might not save much energy, I am hoping it would make the perimeter of the floor a little more comfortable.
We’d use closed cell spray foam to seal and insulate the rim joist. That is one of the steps towards encapsulation, so even if it doesn’t make a big difference now it could still help when it’s encapsulated later.
The house has humidity issues, so doing an incomplete job of encapsulating the crawlspace would make that worse. That’s why I want to leave the venting open until we can get a well sealed vapor barrier in place.
We’re in Colorado, climate zone 5A.
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