Cellulose insulation for Timberframe roof, will it settle?
I’ve been looking over the myriad options presented for insulating a 12/12 pitch roof over a timberframe, and am gravitating towards an assembly like the one presented here: https://www.greenbuildingadvisor.com/article/designing-air-barrier-timbered-cathedral-ceiling. So you fur up the ridge beam by several inches, T&G at bottom, taped drywall for air barrier, cellulose, ijoists, zip sheathing that ties into the wall zip sheathing, then 2x4s for ventilation channel, then sheathing for comp shingles.
My biggest concern is that I’ve been told that cellulose settles. I’ve also been told that they make versions of it that inhibit settling. My question is, how much of a concern is this? Is this something I could potentially DIY install like insulation in an attic? How much of an issue would small air gaps be when I have a foot of cellulose and a ventilation channel above the sheathing? I’ve heard air gaps can cause condensation, but why isn’t that an issue with an attic and the giant air gap there?
cathedral batts and traditional rafters have bridging, rigid foam between rafters had the same issue and seemed liable to shrinking foam causing leaks, 6″+ of foam on the exterior worried my contractor given the 12/12 pitch, ijoists with vent channels built into the flange seemed more labor intensive than just sheathing over the whole thing and laying 2x4s.
thanks for any input!
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