A study by the University of Melbourne has shown that the city could reduce CO2 emissions by over a million kilograms simply by painting the roofs of every building in the CBD white.
We've long know that white is a better reflector of light than black, which tends to absorb - the Mythbusters taught us that. What we tend to miss are the practical ramifications, and the numbers involved in painting things white as opposed to any other colour.
So the City of Melbourne commissioned Melbourne University to conduct a study into exactly what would happen if they were to grab some brushes and get to work on the roofs of the CBD.
The university tested this out by painting the roof of the campus ArtPlay building white. The temperature drop of about three per cent (on a hot day) may, on its own, seem quite small, but when you extrapolate across Melbourne's CBD, the numbers start to hit you.
"Melbourne's CBD has over 3,500,000 square metres of lettable commercial space," says Dr Dominique Hes, lead study author and senior lecturer in sustainable architecture at Melbourne Uni.
"If the roofs of these buildings were painted white, the city could in theory reduce its CO2 emissions by 4.5 million MJ per year, 1.5 million kilos of CO2 or 3 million black balloons".
For older buildings, those that can't be re-insulated or even equipped with ducted air conditioning, these gains are significant. Even newer buildings can save real money by not having to use energy-based solutions like air conditioning to cool themselves down.
Still, three and a half million square metres is a lot of space to paint. They better get cracking.