Does roof color matter much over a well insulated vented attic?
Here’s a roof assembly I’m considering, from ceiling to roof: Gypsum, furring (space for overhead wiring), zip sheathing (air barrier), vapor barrier, energy trusses filled with R-65 cellulose, osb sheathing, roofing felt, batten grid, and through fastened steel roofing. It would have ridge and soffit vents. With a roof like this, with two ventilation layers and thick insulation, does the roof color matter much? I’m looking at a snowy mild heating climate (Rochester, NY area.)
This article pretty strongly says, “If you’re designing and building a new home, keeping an unconditioned attic cooler (in summer) is pretty much irrelevant. Just make sure the ceiling is airtight and fully insulated, and the temperature in the attic doesn’t matter much.” Any conflicting viewpoints and data?
–John
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Replies
John,
With this roof in your climate, your roofing color doesn't matter very much. I can't imagine that switching from white to black, or black to white, would make more than 10 cents difference on your annual energy bill.
Using Zip sheathing as your ceiling air barrier will work, but it is expensive. If you decide to use it as a ceiling air barrier, Zip sheathing is a perfectly good vapor retarder. In any case, your ceiling assembly doesn't need a vapor barrier. So don't install any interior polyethylene.