Unvented and unconditioned attic, is this to code and is this a good idea?
New construction in climate zone 6a, north/central New Hampshire. House specs:
-approx r70 attic consisting of loose fill cellulose in rafters above drywall (the ceiling air barrier)
-goal of 0.6 ACH @ 50 Pascal
The plan is for an unvented and unconditioned attic:
-sealed below at the drywall
-Advantech sheathing on trusses
-roof underlayment either RoofTopGuard (http://www.rooftopguard.com/en/home.html) or heavy felt with Grace Ice and Water first 3 feet on edges, strapped, then metal roof (very simple A frame roof, rectangular 24×32 two story house)
This is a setup that our (experienced) building crew has done before.
We’ve tried general web searches and searching GBA, but what I’ve run into is unvented conditioned attics. We’ve also tried studying the IBC/IRC codes, but are having trouble finding an answer.
With such (anticipated) airtight construction, is it code compliant to have an unconditioned/unvented attic? And if so, is this a good idea and accepted practice in the energy efficient building community?
Thanks for any help you can offer.
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