Spray foam inside rim joist?
I know this is quite commonly done but am I creating a durability issue in my unique situation? My rim joist and main floor joist ends sit upon a 2x6 interior basement wall. The outer 2x8 wall of the PWF basement is filled with MW bats and has "Thermoply" on it's inner face and it's top is 1/2 way up the rim joist. (Lateral soil loads on the PWF wall are transferred to the floor system through the rim joist) The "Thermoply" serves as primary air barrier in the basement and keeps warm air from the PT Plywood exterior basement sheathing. Unfortunately "Thermoply" is very low permeability which leads to my concern about spray foam on the inside of the rim joist as the lower half of the rim joist will have no ability to dry either way. The upper half of the rim joist can still serve as the air barrier without the "Thermoply" giving drying ability to the outside on the upper half of the rim joist. through the mineral wool and vapor open exterior there. To restate my question: Can i, without undue risk of moisture related problems, use closed cell spray foam on the inside of my rim joist if the lower 1/2 of the opposite side is covered by a vapor barrier?
Posted May 28, 2014 3:19 PM ET
Edited May 29, 2014 8:23 AM ET
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