If a floor cantilever past the bearing wall, with no rafters, no vents required. Foamboard and plywood to finish; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/
+1If a floor cantilever past the bearing wall, with no rafters, no vents required. Foamboard and plywood to finish; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/
When the soffit was open, that would have been the time to install rigid board and seal.I appreciate your input! I was reluctant to dive into the project without some guidance, it just simply made no sense to me to have this much air moving into conditioned spaces. We have had a problem with smoke infiltrating as well that gives my wife migraines. Between inversions here in Virginia and neighbors that burn unseasoned wood it is pretty miserable for her.:thumbup:
You misunderstand what I was recommending."Best bet is to install rigid board on the underside as well and then back with a fibrous insulation that is pre-compressed so as not to drop down and cover with an air barrier like Tyvek to hold it in place." -----------------
I don't agree. With f.b. against the sheeting the cavity will be much colder to allow any air leaks around the Tyvek (a water resistive barrier, not an air barrier (they removed that claim after it first came out)) to deposit moisture condensing on the colder joists.
All the links and data are great but real world deployment of that is a different story.Thanks! If I understand correctly now; foamboard next to the floor sheeting, no f.b. on the bottom of the joists. If that is correct: foamboard on the outside of a warmed cavity warms the cavity above dew-point so no vapor retarder is necessary under the drywall (on a wall). It is also a thermal break for the studs. With f.b against the flooring (stopping the room heat), the cavity and studs are much colder, close to the dew-point and temperature of the outside air and are radiation coupled to the ground; if the cantilever is close enough. With f.b. on the bottom, is is similar to an exterior wall (turned on its side) = works best if f.b. is outside of cavity insulation (rather than inside the cavity insulation; next to the heat source) Figs. 1, 2, and 3;