Originally Posted by
Joe Nernberg
Found flex duct through the firewall at 3 areas of the garage.
Even in CA I think that wall between the house and the garage is not a "firewall". It is a wall with 5/8" Type X on the garage side and had a self-closing and latching door, but not a true "firewall".
Even the IRC, which only requires a "separation" wall with 1/2" gypsum board (does not have to be Type X) requires metal duct when duct penetrates through that "separation" wall.