Insulating shiplap vaulted ceilings
Hello! Ive been reading alot of Q&A posts on here as Ive been renovating my house and most recently doing research on best methods for insulating my non vented vaulted shiplap ceilings. Originally the house had shiplap ceilings with a wood shake shingle roof allowing any moisture to seep out wherever it pleased. A couple years ago I ripped off the many layers of old (leaking) roofing when I bought the house (wood shake with 1/2” ply over it and two layers of asphalt 🙄) and installed new 19/32” ply over the shiplap, peel n stick and my new Taylor Metal Roof. Now Im insulating to try and keep the house more comfortable. My rafters are roughly 3x6s spaced anywhere from 16 to 30” apart, mostly 22”ish. I really didnt want to drop my ceilings at all so polyiso was the decision I made with spray foam around it. I was originally going to do solid polyiso between the rafters but recently decided to go with 2” polyiso against the shiplap, Rockwool R15 to fill the rest and a layer of 1”polyiso attached to the bottom of the rafters for thermal bridging. All in all giving me R34 which is more than code here. All seams will be taped and any gaps spray foamed as I go. I was even going to do a separate vapor barrier if needed on the inside of the 1”. Im using foilfaced RMax thermasheath. My question is that once I get it all sealed up and I go to put my shiplap ceilings in underneath all this, how do i keep the screw/nail holes holding the new ceiling to the joist from leaking vapor/air? Thats alot of penetration into the foil facing/vapor barrier. Im in Los Angeles CA so moist air is not a huge concern for the most part here, but Im paranoid about a rotting roof deck. Im up in the higher elevations too and we get snow in the winter as temps dip to high 20s. Our zone is 9a/b I think. Thanks for any helpful tips!
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