Insulation Entirely Above Roof Deck
Ashrae 90 1 defines a roof with insulation entirely above deck as a roof with all insulation 1 installed above outside of the roof structure and 2 continuous i e uninterrupted by framing members table 1 compares prescriptive requirements of the 2004 and 2007 editions of ashrae 90 1.
Insulation entirely above roof deck. The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions. This meets the requirements of section 5 1 4. Insulation entirely below the roof deck. Also the higher the indoor humidity the more insulation is needed to avoid condensation.
Generally more insulation is needed for condensation control in colder climates. Insulation entirely above the roof deck.
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