# Insulating 2x4 attic ceiling rafters help needed



## Windows on Wash (Aug 30, 2011)

I would suggest a larger than 2" rigid foam. Make that the inside insulation layer and go bigger for better overall R-Value.

2" of foam is at most an R-13 plus the additional 2" in the rafter bays is only an R-25 max (if using Poly Iso foam). That will give you the 2" ventilation space as well.


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## Gary in WA (Mar 11, 2009)

http://www.buildingscience.com/documents/digests/bsd-149-unvented-roof-assemblies-for-all-climates

http://docs.google.com/viewer?a=v&q=cache:EJENK_uA9RQJ:www.cr-ar.com/pdfs/Building%2520Code%2520Changes.pdf+R602.3%281%29+2006&hl=en&gl=us&pid=bl&srcid=ADGEESh311Kosslp7jsjp9WhUXxZsgSiyNaWb-eW0YminVwmPUavLlW75BKLoV9em4LFCAydmTGQlkUFOPm8AqHkRP5wLQGQQGkwyzAGtlN4D2DqCiCLwprOpEbvvjeGk6CEhyHiVdtK&sig=AHIEtbRa4Ah_IICPQ3BR1txlzU01V4JQIg

http://www.simplesavings.coop/simplesavings/SIMPLESAVINGS knee walls.pdf

Gary


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