Asked by william mackey

best way to insulate a cathedral ceiling with metal roof , rafters, osb, ice n water up six foot then roof wrap the rest then 1 inch purlins then steel can 1 inch of closed cell work with batt insulation then drywall work.. very confused with all the reading and different answers

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Sean Lintow Sr's picture

Based on codes & best practices you need to use a hot roof system & it does not need to be vented (50" of snow is tipping point) You will need more than 1" of closed cell foam - you need enough air-impermeable insulation at the decking to help prevent dew point issues & most require 2" of CC foam to hit that trigger After you have reached that level then you can consider using other types - with that you should use a blown in product, not a batt type due to voids & compressions that can be caused For more on proper levels, etc...