Sealing/insulating ducts at wall penetrations
I have three duct penetrations to make through exterior 2×4 walls and a 3/8″ rainscreen. Planning to use rigid 26 ga round galvanized duct for all of the 5″ long (or shorter) “stubs” that will pass through the wall and cladding. For diameters I have one 4″ for bath exhaust, one 3″ for woodstove air intake, and one 6″ for range hood exhaust.
1. Anything special about sealing the longitudinal seams where the duct goes through the wall? I guess I wonder about mastic rubbing off on the sheathing ( which I gather should be cut pretty tight to the duct) as well as the siding mounting block. Would foil tape or foil/butyl tape over mastic be beneficial protection? First time working with ducts…
2. Should the ducts be wrapped in a duct insulation in the 2×4 cavity or will the rockwool I plan to insulate the wall with suffice?
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