Another roof assembly question
I am building a 10′ x 28′ house on a trailer. Steel 2×4 framing, 16 on center in both the walls and roof panel. I’m in C zone 3 which calls for R-30 in the ceiling which I’m assuming includes the roof assembly. With the height restrictions at 14′ I have little room on top. This is a shed roof, minimum pitch.
The architect suggests the following:
Inside to outside
1. 1/2″ (min) gypboard
2. 3 1/2 CFS Framing with Rockwool between joists . (R13)
3. 9/16 verco shallow decking 26 g.
4. 2″ rigid insulation (R10)
5. Waterproof membrane underlayment
It’s obvious that I could increase the R value by adding more rigid insulation on top but I’d rather not. If anyone has some brilliant workaround solution for increasing the r value, I’d love to hear it!
Also, will I need a vapor barrier somewhere in the roof assembly or is the membrane on top sufficient?
Thanks always!!
Jayne
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Replies
Maybe a DIY polyiso SIP (plywood on both sides of foam).
Jayne,
Increasing the thickness of the rigid foam layer is the way to go. You wrote, "I'd rather not," but that's what you need to do if you want the R-value.
Thanks you both. I will add an inch. Do I need a vapor barrier or does the waterproof membrane cancel that out?
Jayne,
In Climate Zone 3, there are no code requirements for an interior vapor barrier or vapor retarder.