Spray foam over foam board
Climate zone 4, If there is no problem installing spray foam insulation open or closed cell spray over foam board can the foam board go up against the underside of the heated space plywood sub floor? Or is it better to install the spray foam up against the underside of the heated room subfloor, and fill the balance of the framing cavity with an air permeable insulation towards the direction of the cold side of the cavity? Also would a vapor barrier be necessary? If so where should it be placed? No mech. in the insulated space.
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