THE roofs in Melbourne's city centre are a hotchpotch of grimy cement, cooling units and corrugated iron, with just the odd flash of greenery to soften the concrete aesthetic.
But this palette could change, with new research suggesting that white roofs clad in solar-reflective paint are a cheap way to stop buildings from absorbing heat on hot days, and keep them cooler when the temperature spikes. A joint study by Melbourne University and the City of Melbourne has found that white roofs can make buildings up to 4 degrees cooler inside and allow for 10 per cent more working hours within a comfortable temperature range.
White roofs - also known as cool roofs - have been slowly gaining popularity as an energy-saving measure internationally, but this is the first time that the concept has been trialled in an Australian city.
Last month, the City of Melbourne painted a white roof on its ArtPlay building, a historic railway shed next to the Yarra River, at the cost of $16,000.
The solar-reflective paint has nano particles in it, ceramic beads that act as pockets of air and add insulation to the roof.
Lord mayor Robert Doyle said he would like to see large commercial buildings such as Icehouse and Costco, in Docklands, install a white roof as a retrofit measure, but ruled out financial assistance to building owners or making white roofs mandatory.
''Building owners are not dills, they're always looking at their costs,'' Cr Doyle said.
Although foliage-rich green roofs offer greater temperature reduction, they are more expensive to establish and maintain, Cr Doyle said.
''This is very important, you can just feel it [the heat] when you're in the city at the end of a long hot week,'' he said.
The research found that even on a tall building of 30 storeys, a white roof offered some energy savings and reduced the so-called urban heat island effect, where cities are often 5 degrees hotter than the countryside surrounding them.
''White roofs are a low-cost solution to making buildings more sustainable, particularly our older buildings,'' said Melbourne University senior lecturer and lead researcher Dr Dominique Hes.
The white roof push will form part of the city's beleaguered 1200 Buildings program, which is at the heart of its ambitious bid to become carbon neutral by 2020.
The most recent data shows only 50 buildings have signed up to the program, which aims to dramatically reduce the city's carbon footprint by retrofitting two-thirds of its ageing office blocks.
At the current rate, it will take about 34 years for the council to recruit the further 1150 commercial buildings needed to meet the goal.