Dense-packed cellulose all the way to the facia board?
brentwilson| Posted inGeneral Questionson
I am looking at potentially building a vented cathedral roof with dense-pack cellulose as the insulation. But I want to insulate the roof out to the facia board in order to prevent any chance of heat rising from below the overhangs/covered walkways and causing ice damming. Are there any concerns that I should be aware of with running the cellulose all the way out to the facia board, and then doing facia venting rather than soffit venting for the roof?
Climate Zone: 6B
Snow load: 80 to 100 pounds live load
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Replies
Hi Brent.
This is not a common detail, but I can't see any structural problems with it. And, you'll have to work out the air sealing details so that the cellulose is in an airtight assembly. Perhaps this means sheathing the bottom of the rafter tails and detailing the sheathing as an air barrier as well as caulking the facia board to the plumb cut on the rafter tails? I'm sure that you can figure this part out.
You have to be careful with facia vents and gutters. There is no nice way to make it work without the risk of getting water in there. Facia vent works well for something like a the high side of a shed roof. If you do install them, make sure they are bellow the gutters and there is a kickout flashing above to keep water from getting in.
You can insulate the overhang, but I would still do soffit vents there. Those can be near the edge of the facia, just run the vent baffle down about 2" away from the facia.
Why not use something like coravent at the far edge of the soffit just inside of the facia board. Use the coravent strip as a sort of air duct to connect a soffit vent below to the vent channel above. Another, potentially simpler, option would be two “facia” boards with 2x2s between. The outer facia board would be installed the normal height, but the inner one would be shorter to connect the vent channel to the gap created by the 2x2s, which would allow normal soffit vents underneath.
Bill