Rigid Insulation At Unvented Roof

Rigid insulation used to control condensing surface temperatures rigid insulation installed above roof deck.

Rigid insulation at unvented roof.

Insulating unvented roof assemblies. The quest for greater energy efficiency in buildings has led to increasing interest and need for insulation improvements in hvac equipment more airtight construction new materials and assemblies. Foam free don t stay stuck in the sci finightmare of foam foam foam. In the most recent issue of fine homebuilding martin holladay wrote a piece on insulating unvented roof assemblies.

This section outlines the conditions for unvented attic roof assemblies. Houston tx is located in a hot humid climate region. Unvented roof assemblies should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation. Figure 3 shows the potential for condensation of an unvented roof assembly in houston tx.

We agree that avoiding sheathing rot is critical and that air permeable insulation such as fiberglass or cellulose cannot be used alone. Senior engineer manager at icynene john broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense. Note that table r806 4 indicates the amount of insulation above the roof deck or air impermeable insulation below the roof deck required for condensation control assuming minimum required total insulation as indicated in section n1102 building thermal envelope.