• Cities around the world use cool roofs
    Cities around the world use cool roofs

A cost-benefit analyses of cool roof implementation by the University of New South Wales (UNSW) has found the technology would reduce energy bills, lower indoor temperatures, decrease urban heating and improve the health of vulnerable populations.

The study examined the adoption of cool roof technology across major Australian cities and has been released one month after the NSW government scrapped a previous policy commitment to phase out dark roofs. The policy would have reduced urban heating and energy costs for new homes.

Cool roofs reflect more solar radiation than they absorb so they stay cool in sunlight.

The analyses undertaken by the High Performance Architecture team at the School of Built Environment at UNSW Arts, Design & Architecture was part of a project funded by the federal Department of Industry, Science, Energy and Resources (DISER).

The aim of the study was to  assess the applicability and cost-benefit of using cool roof technology on buildings in Australia and to identify any barriers to adoption.

Chair in high performance architecture at UNSW School of Built Environment, Anita Lawrence, said the study investigated the climatic, social, economic and environmental impacts of implementing cool roofs around Australia.

“We used simulated climatic modelling to understand conditions with and without cool roofs. The results showed urban areas, including Western Sydney, Perth, Melbourne, Adelaide, Darwin and Brisbane, had the most to gain from cool roofs,” Lawrence said.

“The need for cool roofs and other heat mitigation technologies should really be a priority. If not, the cost of climatic change in the next 10 to 15 years will be tremendous.”

 The analyses looked at 17 types of buildings, ranging from low to high rise, commercial to residential and stand-alone to apartment blocks.

Existing buildings with low insulation levels have the most to gain in energy savings by implementing cool roofs. Meanwhile, newer buildings with higher levels of insulation have relatively less scope for energy savings compared to less insulated buildings, but there still savings.

The research found that cool roof technology will significantly reduce cooling energy consumption. Indoor temperatures in residential houses would be reduced by up to 4 degrees Celsius with a cool roof, with the number of hours exceeding 26 degrees Celsius is reduced by 100 hours per summer compared to conventional roofs, which absorb sunlight rather than reflect it.

If the whole of Sydney implemented cool roofs, energy consumption for cooling residential and commercial buildings would decrease by up to 40 per cent in total.

During summer, a building in Western Sydney will require double the energy to cool down compared to the same building in eastern Sydney.

 Besides individual household energy savings, the city-scale deployment of cool roofs also provides collective cooling benefits for entire suburbs, the study found.

With all Australian cities currently suffering from urban overheating, implementing cool roof technology and pavements will reduce temperatures in entire cities by up to two degrees Celsius over the summer period. This is because heat is not transferred from the materials’ surfaces into the atmosphere.

The research also shows that city-scale use of cool roofs would reduce the maximum peak outdoor air temperature, which occurs at 2pm each day, by an average of 1.5 degrees Celsius to two degrees Celsius during summer.

Lower outdoor temperatures mean air-conditioning will run more efficiently. Along with lower energy consumption, energy grids will experience reduced demand at peak times during the summer months, thereby lowering emissions.

Cool roofs can reduce heat-related mortality by up to 25-30 per cent.

Despite a well-established manufacturing sector producing cool roof materials domestically, a lack of legislation, policy support, accreditation standards and awareness is holding the Australian cool roof industry back, the research report found.

If these  barriers were addressed and cool roof technology widely implemented, then approximately 150,000 new jobs would be generated in Australia, according to the study.

It found the infrastructure is already here as Australia has 10 different companies producing cool materials and exporting them all over the world. Cool roof technology is being used extensively overseas.


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