Media contact

Ben Knight
UNSW Media & Content
(02) 9065 4915

New building materials that reduce urban temperatures, and counteract the effects of climate change, will be produced in a research partnership between UNSW Sydney and the University of Sydney.

The so-called super cool roofs, pavements and coatings for buildings reflect rather than absorb solar energy. They can reduce peak temperatures in our cities by up to four degrees, enough to save lives, says Scientia Professor Mattheos (Mat) Santamouris.

“One of the major problems in the built environment is urban overheating, or regional climatic change,” the Anita Lawrence Professor of High-Performance Architecture says. “As our cities heat up, heat-related morbidity and mortality rise.”

In 2020, 593 and 391 people died from heat-related deaths in Melbourne and Sydney respectively, a substantial increase from 289 and 176 in 2007, according to the Australia State of Environment.

Read more: 'Coolbit' aims for personalised comfort advice in specific environments

Countering the urban heat island effect

Overpopulation and rapid urbanisation are transforming our cities into urban heat islands, Prof. Santamouris says. Human activity – waste heat from industry, cars and air conditioners – drives up city temperatures making them significantly warmer than surrounding areas. This affects more than 500 cities worldwide.

“The way we build [also] increases the temperature of our cities. We’re using [heat-absorbing materials like] asphalt, we’re using concrete,” Prof. Santamouris says.

Super cool roofs and pavements by contrast reduce the energy needed for cooling. This in turn decreases carbon dioxide emissions that increase the magnitude of climate change. This makes our cities more economical, environmentally friendly and liveable, he says.

The new-generation materials were tested as part of a study to reduce temperatures in Australian cities, mainly in the frame of an ARC Discovery Project.

The study found that introducing super cool materials with other heat-mitigating strategies, such as increased greenery and shade, could save around ten lives per year per 100,000 residents.

“Under the sun, [with] 42 degrees ambient temperature, the [super cool] materials’ surface temperature was 25. It’s a natural air condition without expending any energy – super cool materials,” the energy physicist says.

“And all these new technologies and new materials have been developed here in Australia.”

Graphical diagram of the impact of the application of cool material on cities

Application of cool material in cities can result in a reduction of peak ambient temperature. Source: Image: Supplied.

Promoting energy economy with government

Prof. Santamouris and his team are partnering with the Department of Industry, Science, Enterprise and Research (DISER) on two projects to promote energy efficiency in the built environment.

The team will provide cost-benefit analyses and scientific documentation on the adoption of cool roofs in Australia, and ways to improve energy efficiency in new and existing commercial buildings, such as office buildings, aged-care facilities, hotels, childcare and shopping centres.

With around 40 percent of the total energy consumption in developed nations attributable to buildings, there is huge potential for impact, Prof. Santamouris says.

“The reduction of energy use and associated greenhouse gas emissions through energy conservation measures is vital to achieving energy and climate goals in the cities,” he says.

Read more: A 'bad economic bet': What will climate change inaction cost Australia?

Princely project a win for Australian tech and knowledge exchange

Prof. Santamouris is applying his research to reduce temperatures in Riyadh in Saudi Arabia, one of the world’s hottest cities. The Royal Commission of Riyadh has engaged his team to develop an all-pervasive heat-mitigation plan, the largest of its kind.

The project recognises Australia’s world-leading research and technology in the field, and delivers significant health, sustainability and economic outcomes. They use computational tools empowered with rich urban datasets to model building performance at the urban scale, identify energy retrofits and inform urban planning.

Extensive aerial monitoring using airplanes and infrared technologies, performed by industry partner National Drones, will map the city’s thermal conditions. While large-scale high-resolution simulations of the city will evaluate different scenarios to decipher optimal strategies.

The project also considers the city’s vegetation, water, ventilation and introducing super cool materials. The team is coordinating similar studies for the cities of Dubai, UAE; Kolkata, India; and Kuala Lumpur, Malaysia in collaboration with local researchers.

Scientific graph of heat mitigation in Riyadh

Cool materials were applied in the mitigation case and a reduction of the ambient temperature was observed. Extracted from the project report for Cooling Riyadh. Image: Supplied.

A more equitable energy blueprint

Energy conservation also has a flow-on effect to equity, Prof. Santamouris says. Today 20 percent of the population in developed countries cannot afford to cover their energy needs due to low income and low-quality housing, he says.

“The temperature difference between Eastern and Western Sydney during summer, for example, is up to 10 degrees. In a distance of 60 kilometres, that’s tremendous,” he says.

“This has a tremendous impact on the quality of life of people in Western Sydney. They spend almost 100 percent more energy on cooling. They have much higher mortality rates.”

The less energy we need, the greater the thermal satisfaction of all people, he says. And that is the end goal for him. The most powerful research pivots on pragmatic altruism, he says.

“Research must advance knowledge, help solve existing problems, and cover existing knowledge gaps to better the quality of life,” he says. “It must advance the global good for the improvement of society, to protect the lives of citizens.”

Prof. Santamouris is ranked the top most cited scientist for building and construction globally for 2019 and 2020 in the Meta-Research Innovation Center at Stanford. He and his team are involved with more than 200 large-scale heat-mitigation projects around the world in Europe, the Americas, Asia, and Australia.