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There are a selection of insulation products that can be used with skillion roofs to achieve great thermal performance, all the while maintaining a suitable air gap between the roof underlay and insulation.

In skillion roofs, the roof space is generally inaccessible, the insulation thickness is restricted by the rafter depth and there should be a 25mm gap between the top of the insulation and the underside of the roof underlay.

The standard celling products which provide high R-values cannot be used in a skillion roof due to the thickness restriction and need to maintain the required clearances. If used, ventilation can be restricted and may result in compression of insulation effectively reducing the R-value performance and potentially creating problems due to the lack of ventilation.

Pink® Batts® has an exclusive range dedicated to insulating skillion roofs - Pink® Batts® Skillion Roof R3.2 with maximum thickness of 115mm and Pink® Batts® Skillion Roof R3.6 with maximum thickness of 165mm. The range is designed to be used in skillion roof constructions while still achieving the minimum 25mm clearance between the roof underlay and the top of the insulation in:

New buildings and retrofits of existing ceilings.

Modern ‘lean to’ style extensions on existing homes. Low profile roof design and restricted roof cavities

Cathedral style roofs and raked ceilings are generally skillion roof constructions where the ceiling line and roof line are in parallel

Besides the skillion range, the wall range of Pink® Batts® glass wool insulation also makes for an excellent alternative where you want to achieve higher R-values in the same thickness. Check our recent skillion retrofitting job where we installed Pink® Batts® Ultra® R4.0 Wall to meet the requirements of client.  


The table below shows the maximum R-value that can be achieved in a skillion roof for a given thickness in Pink® Batts® glass wool range:

Insulation Thickness (mm)

Rafter depth (mm)

Product or product combination



Pink® Batts® Ultra® R4.0 wall 



Pink® Batts® Skillion Roof R3.6



Pink® Batts® Skillion Roof R3.2



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