Vapor diffusion ridge vent worthwhile for a conditioned attic?
I’m in the middle of having a new roof constructed for a conditioned attic, with the following layers: rockwool (inside attic between rafters), existing skip sheathing, FR10 fiberglass slipsheet, 3″ polyiso insulation, plywood sheathing, FR10 fiberglass slipsheet, G40 underlayment, lightweight concrete tile. I’m in climate zone 3, Southern California. I was reading this article,
and found the “vapor diffusion port” (vapor diffusion ridge vent) section interesting. I didn’t think of this before. Now is my last chance add this feature. Is this something worthwhile to consider? Where would the roofer obtain a special material that allows vapor to exit but prevents airflow? Any particular brands, item numbers of this special material?
My initial thought is that this may be overly complex and I can just allow a little bit of the air conditioning/heating into the attic space. Or maybe this is useful? Right now it wouldn’t cost that much to add because the roof is nearing sheathing stage.. except for trying to get some exotic diffusion material.
Also would this have a big effect to reduce the R value of the assembly?
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