Further to my advice on the changes to NCC Part J, we now need to consider roof colours a bit more closely when following the Deemed to Satisfy provisions.
Now in climate zones 1, 2, 3, 4, 5, 6 and 7, the solar absorptance of the upper surface of a roof must be not more than 0.45.
For your reference I have included a chart below of standard Colorbond colours with their respective absorptance values and a PASS or FAIL.
The classification of colours in the NCC is based on solar absorptance, which is the inverse of solar reflectance, expressed as a ratio between 0 and 1. A Solar Absorbtance value of 0 indicates that a roof absorbs none and a value of 1 indicates that a roof absorbs 100% of the incoming solar radiation.
By the way, zincalume passes with an absorptance of 0.35.