Rigid Insulation At Unvented Roof

In the most recent issue of fine homebuilding martin holladay wrote a piece on insulating unvented roof assemblies.

Rigid insulation at unvented roof.

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. 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. Ratio of r value between rigid insulation and batt insulation is climate dependent. Figure 3 shows the potential for condensation of an unvented roof assembly in houston tx.

Houston tx is located in a hot humid climate region. Foam free don t stay stuck in the sci finightmare of foam foam foam. 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. We re big fans of fine homebuilding.

If you don t want to use sips or nailbase read this article tolearn the four basic approaches to insulating unvented roof assemblies. This section outlines the conditions for unvented attic roof assemblies. Rigid insulation used to control condensing surface temperatures rigid insulation installed above roof deck.