Building a new commercial building in Climate Zone 5? Did you know that roof colour matters?
A change to the 2012 edition of the Building Code of Australia varies the total roof R-value required for compliance. This is expressed in terms of Roof Upper Surface Solar Absorptance.
Climate Zone 5 contains the eastern half of Sydney and the coastal strip north and south of Sydney. In this area, a building with a light colour (Solar Absorptance of not more than 0.4) must achieve R3.2 for the roof/ceiling system. Depending on the roofing materials used, this often translates to requiring more than R2.8 of insulation. This requires thought in design detailing to ensure the thickness of insulation can be accommodated.
However, if a medium or dark roof colour is used the required system R-value increases to R3.7 and R4.2 respectively. This can translate to insulation in the order of R3.3+ or R3.8+ for the two cases. So, check the Solar Absorption value of the roof colour you plan to use. In the Colorbond range for example, the table below shows a variety of colours and their respective Surface Solar Absorptance value.For more details refer to the Colorbond web site.