Insulation in roof
I am looking to insulate the roof plane of a small library addition in Coastal Maine. This area is over the entry and librarian station in a section that connects our super-insulated addition (using dense pack cellulose in a double stud wall construction and dense pack cellulose in roof trusses) to the existing building. It has only 2×10 rafters. Can I specify dense pack cellulose between the rafters, Zip system sheathing on the roof, and then 1 or 2 layers of a new product: 1″ rigid VIP, Vacuum Insulated Panel by Kingspan, on the underside of the rafters and get the r-value needed? I need at least r-50+, preferably r-60. Then where does the vapor barrier occur? I understand that Zip panels have an integrated vapor barrier. Will I be introducing another vapor barrier on the under side with with the VIP panels?
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