Skillion roofs pose a unique challenge for achieving the new higher R-values, particularly via the Schedule method, under the 5th Edition of H1.
Comfortech® have specifically developed a Pink® Superbatts® Skillion Roof R7.4 that will allow a single layer solution to the Schedule method R6.6 requirement, it is however limited to a 290mm deep rafter depth. If the rafter depth is less than 290mm, we recommend a two-layer solution, using a first layer of R6.0 at 235mm thickness between the rafters and a second layer of Pink® Superbatts® Skillion Roof R1.0 (at 40mm thickness) to be installed below the rafters, between the ceiling battens, with rafters at 900mm centres this will meet the required R6.6 construction.
Single Layer Skillion Solution
If you are specifying a metal tile roof, and therefore running the roof underlay under the purlins, you will need to raise the purlins to maintain the 25mm air gap between the underlay and the insulation, as required by NZS 4246.
Double Layer Skillion Solution
If you are specifying a metal tile roof, and therefore running the underlay under the purlins, you will need to specify a 290mm rafter to maintain the 25mm air gap required by NZS 4246.