For a better floor
I will have a contractor build the shell of a house (including windows and shingles) for my dear, old Mom.
I would greatly prefer to condition the crawl space, even in my zone 4 marine (Vancouver, WA), but our county is deemed radon hot and conditioned crawls are not allowed.
Spray foaming the floor (9 1/2″ TJI) to r-30 is out of the budget which leaves fiberglass batts, or a blown in product held up in place with some type of battens.
I could make the subfloor the air barrier by using Fast Flash or tape on the seams and filling and sealing penetrations and:
A. Have an insulator string up batts and hope for the best.
B. Gravity-fit rigid foam or OSB/plywood between the I-joist webs, on the flanges to prevent batts from sagging over time and to greatly reduce the loss of R-value when the air blows past the fiberglass.
C. Attach rigid foam or OSB/ply under the joists and blow in insulation, one section at a time.
Owens Corning just emailed that the Foamular isn’t designed for this and that it might need a 15-minute thermal barrier such as sheetrock. Avoiding XPS is fine with me, but “What’s the Better Way?”
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