I am about to replace the roof on our house with a new colorbond roof (old one was done badly when an extension was added to the house before we purchased it and is leaking in multiple places). I am trying to find out how much difference the colour we choose actually makes to the inside temperature of the house. I have seen the data on the colorbond website that shows how much each colour absorbs but there seems to be very little information on how much difference that actually makes inside the house if the roof is lined with the Air-cell (or similar bubble/reflective) insulation. Does anyone know of any studies that have been done on what the real-world difference is between lighter and darker roof colours on internal temperatures assuming correct insulation? The reason for the question is my wife would prefer a darker grey colour and I am trying to convince her that the lighter colour will save us money but she has asked the ackward questions of "how much per year" are we likely to save on cooling costs or "how much cooler will it be" with the light coloured roof and I cannot find any information to back up my argument!
We are located on the Sunshine Coast in Queensland (just north of Brisbane) and tend to be in the house most days so currently in summer the aircon gets a bit of a workout (I think this is partly due to poor insulation under the current roof but as we have no ceiling space I can't do anything about that until the roof is replaced at which time new Air-cell will be installed)