Guest User
5/14/2010
I am in the process of getting quotes from a few folks and have a question regarding ventilation. I will be installing metal roofing (hopefully standing seam-cost dependent)over a shingle roof. The roof is insulated, but where there are recessed lights, I lose heat. I was thinking it would be a good opportunity to address this issue by laying down 1" "Dow blue board" between the purlins.Should I use 2x4 purlins to allow for ventilation between the the "Dow board" & metal? One of the contractors says he doesn't believe ventilation is necessary (mt gut disagrees). What do you think? BG
Guest User
5/14/2010
This is really more of a thought regarding my original post/question...it occurs to me that (now that I think of it) that if the roof that's installed is "standing seam", there will be no through ventilation possible anyway given the purlins will be running horizontally. That said, will I be creating a problem if "Dow board" is installed regardless of thickness of the purlins...1x4 (rough cut) or 2x4. Any insight would be appreciated! Thanks BG
Eric Novotny
An informed customer is the Best Customer!
5/14/2010
If there is any chance of moisture migration through the substrate of the roof that can collect on the underside of the standing seam, you better have it ventilated. If you address all the envelope breaches between the conditioned and unconditioned space, attic ventilation is unnecessary. The question is whether or not you an get to all of them. You better be certain.
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