Installing Polyiso in attic living space
I am working on a renovation of a 1940's house in Norfolk, VA. I want to properly install the recycled 2.5" polyiso insulation I have in my attic. The attic is used as living space. I have 2 x 6 rafters and want to increase the R value as much as possible by cutting sheets to fit between the rafters and then sealing them with spray foam to replace the R 19 bat that was up there.
It seems there is an ongoing discussion on the use of vents or not. My soffits do not have vents, and I would only have 1/2" left over after I put the polyiso up. My reading of the IRC code (2009 IRC 806.4) is that the boards could be installed as an unvented roof assembly if the polyiso boards were pressed tight against the underside of the roof sheathing and that no ventilation would be used, as well as no vapor barrier on the interior side. I am wondering if I am correct in this interpretation, and if anyone knows the up to date specifications on this issue?
Posted Sep 30, 2012 2:00 PM ET
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