Can a rainscreen become a chimney for fire?
I have a client who is concerned about fire in a rain screen I recently put up to go under siding.
This is a wall of rough cut 1 inch board sheathing covered in typar and taped at all penetrations and seams. The typar is the primary air barrier. The rain screen is 1X3 (3/4 thick) strapping running vertically every 16″ oc. The bottom is open and covered with fiberglass mosquito netting and the top is open to the soffit. The soffit is not vented into the attic. I am planning to insulate with dense packed cellulose. The siding will be vertical grain unpainted cedar.
My client is concerned that the 3/4″ space between the siding and the sheathing will be able to act as a chimney to spread fire, should a fire occur. I’ve never seen anything written about this. Any ideas?
This building is in southern Vermont, so there is no great danger of wildfire.