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Should we paint the town white? Cool roads could cool our cities

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With the looming El Nino weather system threatening to deliver longer and even more frequent heatwaves, a Sydney-based project is investigating the use of lighter-coloured bitumen on roads to reduce urban temperatures by as much as 7°C.

The Cool Change Cities Project, led by sustainability expert Michael Mobbs, will build a trial “cool road” in Chippendale, NSW, to compare before and after data on its surface temperatures, and any impact these changes might have on local energy bills, public health, and on surrounding biodiversity.

According to Mobbs, a “cool road” uses pale surfaces like concrete, a resin mix like bus lanes, or pale rocks shaved to present a pale surface.

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A cool road: pale road surface, mix of edible and decorative trees and plants, shade over 50% of the road

And while it might sound cosmetic, it is considered a more and more important ingredient in the effort to lower the temperatures of our cities, which have been found to exacerbate extreme heat by between 4-7°C, especially overnight.

Speaking on ABC’s Lateline on Monday night, Professor Liz Hanna, an environmental health expert from the Australian National University, said the use of black roads and roofs in new housing developments – surfaces that could be 30°C hotter than forecast air temperatures – made no sense in Australia’s climate.

“We drive around and shake our heads in dismay at the silliness of this, the cost of retrofitting these houses and the poor, miserable people in the future who will have high electricity bills because they’ll be forced to cool their houses artificially,” she said.

Roads, in particular, which take up between 24 to 35 per cent of the landmass of our cities, are believed to have the effect of increasing the temperatures in suburbs, affecting power consumption and tree growth.

“If we are to do anything about our climate we must do something meaningful in our cities,” said Mobbs, director of the Cool Change Cities Project. My vision is to cool Australian cities by 2 degrees by 2020 by quite simply building cool roads.”

Citing an example from New York, Mobbs said a pale road retrofit costed at $58 million produced a saving in energy bills of $57 million alone. The research found a one-degree increase above 20 degrees increased energy use in the city by 3300 MW.

“Just imagine how transforming this could be for the people of Western Sydney, the Northern suburbs of Adelaide or the people in suburbs and towns in Western Australia,” he said.

“The NSW government, have been highly supportive of my vision – we’re discussing solutions for wider studies and rollout across the State. Other parts of the country are looking on with interest and we are in discussions with some corporate players who can immediately see the benefits here.”

 

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  • Gongite

    This is a great common sense step to address urban heat islands and make our cities less sweaty in summer. I really hope it gets rolled out across the state, and the country!

  • Chatteris

    Interesting to see if any nay-saying politicians oppose it because it’s part of the climate change discourse and to admit to urban warming would be tantamount to admitting to global warming!

  • Alan Baird

    Nah, I prefer black tiled roofs ‘cos they’re so NOW. Plus the energy companies would surely see they’re good for profits so it’s a win-win situation. I love to hear an air conditioner really work (nay, groan!) every summer. Another idea is to have more houses set up with large, western-facing windows. Very popular. I have lost count of people who see no connection between using electricity, thick habits and power bills. You don’t have to be stupid but it does assist considerably.

  • Guest

    Unfortunately, the science about reflective pavements isn’t quite as clear as Mr. Mobbs is stating. There’s been a lot of looking at what cool roofs do, but reflective pavements don’t just bounce solar energy back into the atmosphere; they bounce it back into buildings and cars and people. Arizona State University has identified multiple unintended consequences associated with relying upon reflective pavements to mitigate the urban heat island effect — http://ncesmart.asu.edu/news/unintended-consequences . UHI is endemic to the built environment and the replacement of vegetation with structures. Green roofs, green walls, tree boxes, and other ways to get more plants back into the urban space will do more to improve UHI than simply painting roads and car parks white.