Classification of COLORBOND® steel colours for NCC and BASIX
On hot sunny days, light coloured (low solar absorptance) roofing material commonly keeps cooler than darker coloured (high solar absorptance) roofing material. To recognise the cooling benefit of lower solar absorptance roofing, some building regulations have incorporated it as an energy efficiency design parameter. Lower solar absorptance roofing qualifies for a roof insulation concession under prescriptive regulation in most climate zones in Australia1 . Alternatively, choosing low solar absorptance roofing lowers the calculated cooling (when using building verification software for compliance) which may help achieve higher performance or lower building costs2.
BlueScope has provided solar absorptance values and NCC and BASIX classifications for 22 standard colours of COLORBOND® steel as well as for COLORBOND® steel Matt, COLORBOND® Metallic steel and more. Please refer to the COLORBOND® steel colours page for a complete list of the values.
Colour Classification in Accordance with the NCC3
The National Construction Code (NCC) has classified roof colours based on their solar absorptance, as Light (L < 0.40), Medium (M < 0.60) and Dark (D > 0.60).
Colour Classification in Accordance with the New South Wales BASIX
The New South Wales Building and Sustainability Index (BASIX) has also classified colour into Light, Medium and Dark based on their solar absorptance, however, the range of values varies to that of the NCC. The BASIX classification is Light (L < 0.475), Medium (M < 0.7) and Dark (D > 0.7) categories.
The classification of colours in both the NCC and BASIX is based on solar absorptance (SA). SA is the proportion of the total incident solar radiation that is absorbed by the roofing material (the remainder is reflected) and is expressed as a ratio between 0 and 1. A roof with a lower solar absorptance will reflect more heat than a roof with a higher solar absorptance and may keep the roof space and dwelling cooler on a hot day4.
For further information please refer to: