Hi y’all, I’m puzzling over how to do roof insulation in the “garage” we’re going to build. I had figured on a vented eve/ ridge, tall heeled energy truss/ blown cells.
After reading here and other reccomended sites, I’m thinking a non vented hot roof might make more sense.
Target is to heat this place for cheap once completed. It’ll house my workspace and a place for cars.
Some details:
Southern Idaho
2600 ft. divided into two spaces.
Radiant Slab
6″ SIP Walls
9 large Sun Tunnels
3/12 pitch hip roof, trusses, exposed rafter tails, comp. shingles. I might add that for a number of reasons, SIPs is not a possibility for roof.
From what I can gather, moisture transmittal/mitigation is one of the main concerns in venting an attic. There is a bathroom but no shower so I’m thinking moisture is not much of an issue. The other factor is shingle life, which appears to be shortened somewhat, but not a bunch.
Eliminating venting would solve the fussy detail of venting the bird blocks between rafters, and also the limited venting of ridges due to hips.
My thought was to foam the underside of roof deck before rocking the ceiling. Could even do a combo with blown cels, I suppose. Would like to end up with R-40.
Does a “hot roof” make sense here?
PJ
Everything will be okay in the end. If it’s not okay, it’s not the end.
Replies
Yes to hot roof.
Joe H
http://construction.tyvek.com/pdf/AWInstRafterCapK14124.pdf
Thiss allows you to vent and insulate, while keeping water off your rafters if it eventually penetrates. Since you are using trusses on a shallow roof, you might as well just pack it tight with cellulose.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Giving myself a bump here. Anybody else want to chime in?
PJ
Everything will be okay in the end. If it's not okay, it's not the end.