Insulation Entirely Above Roof Deck

Insulation entirely above the roof deck.

Insulation entirely above roof deck.

Roofing with insulation entirely above deck a roof with all insulation 1 installed above outside of the roof structure and 2 continuous i e uninterrupted by framing members. 2007 levels are based on today s energy. Placing all of the iecc code required insulation above the roof deck with a vapor retarder will provide acceptable hygrothermal performance in all climate zones figure 7. 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.

The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions. Also the higher the indoor humidity the more insulation is needed to avoid condensation.