The roof solar absorptance is the proportion of the total incident solar radiation that is absorbed by the roofing material (the remainder is reflected).
A roof with a lower solar absorptance will reflect more heat than a roof with a higher solar absorptance, and will keep the roof space and dwelling cooler on a hot day.
Typically, the solar absorptance is related to the colour of the roof as shown in the table below. Where the actual solar absorptance is not known, select the appropriate colour category: light, medium or dark.
| Solar Absorptance | Typical Colour |
|---|
| < 0.475 | Light |
| 0.475 - 0.7 | Medium |
| > 0.7 | Dark |
Roofing manufacturers have been advised to provide a solar absorptance value for the colour you choose to enable certifier to match it against the range specified in the commitments on the BASIX certificate.
Spectrally selective surfaces can reduce the solar absorptance for a given roof colour.
Roof colour and glare
While a lighter colour roof will have higher heat reflection (or lower solar absorptance) than a darker roof, it will not necessarily produce more glare or light reflection. It is possible to get a roof with low solar absorptance AND low light reflection. Users should investigate these options where glare for neighbours may be a concern.