Cathedral ceiling technique explained?
I posted a full description in the insulation and energy forum, but I am also looking for the building details for the unvented cathedral as seen on page 68 of the article posted below. The #3 Unvented roof. We are in the SF Bay area.
My roof has 6x10 beams, covered by 1 1/2" T&G. In the re roof, this will get sheathed with plywood, then I'll add two to three layers of 2" polyiso. I am hoping for 2 layers to save money. Will that give me a true R30? I thought it was only R 6.5 per inch. On top of that will be another layer of 1/2 ply.
The architect is specifying laying a grid of 2x6 lumber on top of the plywood and then adding the insulation in between.
My question is, can't we do without the 2x6 build up and just use long screws to attach the 2nd layer of plywood through the foam? Does anyone have a detail or pictures of this?
Can I run the pipes for my fire sprinklers in this buildup without worrying about condensation? I would place them just above the first layer of sheathing.
What is the advantage / disadvantage to having a hot roof? I assume we could make this a vented roof if we added a layer of furring strips above the top layer of foam, and below the top plywood layer? is an unvented roof a bad thing?
Posted Sun, 09/22/2013 - 00:08
Edited Sun, 09/22/2013 - 05:33
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