Can cedar breather be used as ventilation beneath a deck for asphalt shingles? It’s over an attic spray foamed onto the underside of the old skip sheathing. Ridge vent would be used for topside exhaust and I think the rakes would need a furring strip down their length to seal off the breather to force proper airflow to be drawn from the eves?
In theory it should work.I was at a ventilation seminar a couple years ago and the guy mentioned that spray foaming up against the deck is a no no ,due to moisture at the dew point,the wood will rot.Cedar breather should take care of that.I think you would also want a vented drip edge.
So much about theory-heres the problem,you may not have a shingle warranty,unless you get permission from the manufacturer.That approved deck clause in the fine print.You should make a sloped 4x8 test deck to see if the mesh will support the shingles,test nail pull when you walk on it,and document it for the manufacturers.
I’ll be keeping an eye on this one,let us know what you find
The breather would be decked by 1/2 OSB and the eves drip would be kept a 1/2" away from the decks lower edge for air flow up into the breather. Attics insulated this way are accepted by CT and others when sprayed directly but for awhile it was not.
Hi me again.
I forgot to mention a project that I was involved in ,and one a friend of mine came up against.These were a post and beam type homes that had strofoam inbetween the beams with shingles over top.A poor design.What we did is nail furring strips to the beams ,then sheeted it with ply,install vented drip edge,shingled and installed ridge vent.We achieved a air space and got an approved deck.
A bunch 2x4’s is cheaper than cedar breather
I would install vented drip edge to stop insects from getting into the breather
What OSW said.
Bugs would be right at home in that mesh. I could see mud wasp jamming the entire leading edge! It’s a tall home in a very high wind area so the thinking was thin breather would keep the deck close enough to the skip sheathing and rafters so that it would also contribute a lot to racking resistance and tighten the old structure up. furring is a lot cheaper though for sure.
OSW-here’s some ventilation and unvented deck research: thermalsealexperts.com/design11.php
Pretty interesting-Montana has been doing it unvented for years without problems.
If you were to use cedar breather under asphalt shingles you would probably need to hand nail the shingles, a nail gun will blow through every time.
The breather would be between the old skip and new OSB deck.