I note that B1D3 in Vol Two of the NCC code now requires certain Class 7b buildings to be designed for an additional notional permanent roof load of 0.15kPa to allow for the addition of solar panels. No other guidance is added.
This raises several matters in my mind.
Why is the NCC being used as the mechanism to define building loads outside of adopted Australian Standards. Is the system that broken.
I agree that guidance on how to allow for roof mounted solar panels is needed and should have been in the Australian Standards long ago.
The NCC wording leaves many aspects of designing for possible solar panel loading unanswered.
If the 0.15kPa permanent load is applied, does the 0.25kPa live load still get applied over the same area?
Members thoughts would be appreciated.
The NCC appears to indicate that the 0.15kPa is the minimum load to be accounted for, so it could be argued a higher value may be required. The other thing is the load is listed as a performance requirement, whereas the Australian Standards appear in the DTS section of the NCC.
Compliance with the Australian Standards is not necessary to meet the performance requirements of the NCC. I suspect that this is meant to close off the possibility of this load not being considered at all should someone choose to say that they don't consider the load under a performance solution.
Regarding the live load, the commentary to the AS1170.1 mentions that the 0.25kPa accounts for stacking of materials and local accumulation of hail. You could argue that hail could accumulate underneath the solar panel arrays and potentially get stuck underneath for a short period of time.