Cold floor over crawlspace
Problem: My house is uncomfortably cold during the winter, especially the floors. Running the heat leads to excessive dryness.
Located in Charlotte, NC (Zone 3)
Built in the 1970’s, on a sloping lot.
Sits on a crawlspace that varies from 3’ to 8’ high.
Has a large number of casement windows
Has a cathedral ceiling in the living room, which is by far the coldest in the winter.
Walls are insulated with fiberglass batts, sheathed with particleboard and vertical cedar siding. No housewrap.
Floor is insulated with fiberglass batts that aren’t in great shape
We’ve already laid down plastic in the crawlspace, plugged the vents, and added a dehumidifier. This was done to prevent mold.
I’m open to other suggestions, but I think the most economical solution would be to deal with the cold floor. The crawspace gets cold due to the tall uninsulated walls. I think I have two options for fixing this:
Option 1: Spray foam the crawlspace walls. Rigid foam probably won’t work, because the walls aren’t flat (CMU pilasters with brick infill). Unfortunately the high side of the crawlspace has some drainage issues, and causing water to travel beneath the poly which covers the dirt floor. I’d probably have to rip out some mature bushes and install a french drain to fix this. Also, spray foaming the band sill is risky, because my deck ledger is not properly flashed.
Option 2: Attach 1” polyiso to the bottom of the floor joists. The advantage is that i could probably do the work myself. One disadvantage is that there will still be heat loss through the ducts. Also, it could get tedious taping all the joints, notching around footings, and dealing with Romex and piping that is attached to the floor joists.
Any comments on my best option are greatly appreciated.
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