Implementing cool roofs across Sydney’s residential and commercial buildings would slash 40 per cent of the energy used to cool buildings in summer, new research from UNSW has found. 

UNSW’s latest study adds to a growing body of research that shows implementing cool roof technology and pavements across cities will reduce peak daily temperatures by an average of 1.5 to 2 degrees celsius during the summer. This will reduce energy bills, lower urban heating, and protect the health of vulnerable populations.

In April, NSW Planning Minister Anthony Roberts scrapped a proposed planning law called the Design and Place SEPP, which would have phased out dark roofs in favour of cooler, lighter coloured roofs on new homes. 

The SEPP included an update to the state’s apartment design guidelines that would have encouraged the construction of cooler, more energy efficient apartments, with low-carbon building materials, good ventilation, green spaces, and access to sunlight.

Unlike dark roofs, cool roofs reflect more solar radiation than they absorb, and as a result they stay cooler on hot days. 

Indoor temperatures in residential homes are likely to be around 4 degrees celsius cooler with a cool roof, and the number of hours exceeding 26 degrees celsius are reduced by 100 hours per summer compared to darker roofs.

The analyses looked at 17 building types from low to high rise, commercial and residential, to find that existing buildings with less insulation have the most to gain in energy savings by implementing cool roofs. 

With Australian cities increasingly suffering from urban heat islands and overheating due to climate change,  cool roofs reduce reliance on air conditioners and lead to lower bills for residents.  

Along with a 40 per cent reduction in the energy used to cool buildings, this will mean Australia’s energy grids will experience reduced demand at peak times during the summer months, leading to lower emissions.

Scientia Professor Mattheos Santamouris from UNSW’s School of Built Environment said Australia has an established domestic manufacturing sector that produces cool roof materials, but a lack of legislation, policy support, accreditation standards and awareness is holding the industry back.

“If the barriers were addressed and cool roof technology widely implemented, then approximately 150,000 new jobs would be generated in Australia,” Professor Santamouris said.

Professor Santamouris said a building in western Sydney will require double the energy to cool down compared to the same building in eastern Sydney. 

“Cool roofs can reduce heat-related mortality by up to 25-30 per cent. They will also help address energy poverty – an issue severely impacting the quality of life of low-income households.”

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