MAM derating due to small air gaps?
Posted: Mon May 25, 2020 5:07 am
Building a ground-up studio. Designing so I can use the outside building envelope (sheathing) as outer leaf. Double 3/4” sheathing on outer wall sealed up real tight, with a 3/8” “rain screen” gap between sheathing and 1/2” ply cladding, open at bottom and top so air can flow through to dry the assembly, with 3/8” plywood furring over studs for spacing/nailing cladding. I’m assuming I don’t get to count the 1/2” cladding as part of my outer leaf as there is an air gap of 3/8” between sheathing and cladding. Note, this is double wall construction and the inside leaf will be 12” away from the back side of the sheathing. Can anyone tell me how to figure de-rating of TL through assembly due to this small air gap? Will I just end up with a dip in TL around the cavity resonant frequency of that 3/8” gap? Thx guys.