UNSW study offers possible answer for desert city temperature control

by Helena Morgan
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The university’s findings, available in the newly launched online journal Nature Cities, reveal that a judicious selection of cooling technologies and techniques can decrease the temperature and energy costs of Riyadh, Saudi Arabia.

Saudi Arabia’s capital city, and other hot desert climate cities like it, may experience a 4.5 degrees celsius decrease in temperature, if highly reflective and ‘super cool’ building materials – manufactured by UNSW-based research team, the High-Performance Architecture Lab – are combined with irrigated greenery and energy retrofitting. 

Completed via joint efforts with the Commission of Riyadh, UNSW’s study marks a new era in climate-responsive urban planning as a world-first investigation into the rewards of heat mitigation technologies. 

UNSW Scientia professor and specialist in heat reduction technology Mattheos Santamouris says cities would be wise to embrace heat migration technologies. 

“Heat mitigation techniques reduce urban overheating, decrease the reliance on cooling needs and ultimately improve lives,” he says. 

Concrete jungle effect

A 2020 study revealed that chronic urban heat – caused by climate change and unstoppable urbanisation – impacts over 400 cities worldwide and results in extensive energy consumption and severe heat-related illness and death. 

Riyadh is one of the hottest cities in the world and records temperatures as high as 50 degrees celsius in the summer. 

Santamouris explains the problem lies in cities such as Riyadh continuing to place large concrete and asphalt surfaces in densely populated areas – when coupled with car pollution, industrial activities and scant green spaces, temperatures skyrocket.

How do we cool the hottest cities in the world?

UNSW researchers completed large-scale cooling climatic and energy simulations of the AI Masiaf precinct of Riyadh and evaluated the energy performance of 3323 buildings in urban areas under eight separate heat mitigation scenarios, to determine how best to tackle heat reduction in desert cities. 

From considering multiple combinations of reflective, rather than absorbent, building materials, vegetation types and energy retrofitting options, researchers concluded it is possible to lower the outside temperature of a city by almost 4.5 degrees in the summer. 

Additionally, cooling energy conservation would be improved by up 16 percent.

“Implementing the right combination of advanced heat mitigation technologies and techniques makes it possible to decrease the ambient temperature at the precinct scale,” says Santamouris.

UNSW researchers implore construction and engineering decision makers in desert cities to use reflective materials in buildings and increase the planting of irrigated trees by more than double. 

However, Santamouris warns against an over-zealous embrace of urban cooling techniques, particularly those that are not rooted in scientific optimisation such as non-irrigated greenery, as this only compounds the problem and warms the city. 

Avoiding an over-dependence on cooling measures 

Researchers also discovered that pairing reflective building materials with energy retrofitting measures such as insulation, solar roof panels and double glazed windows, can plummet cooling demands by 35 percent. 

Professor Santamouris envisages a reduction in energy demand for Riyadh as both cost-effective and nurturing to the needs of inhabitants. 

“This would help further reduce costs associated with cooling for the city, while improving the quality of life for the local population,” he explains. 

A win for city health and wellbeing 

Heat mitigation technology cares for the city’s inhabitants by increasing thermal comfort, minimising heat-related health illnesses and slashing pollutant density – producing a happier, healthier and more productive city, starting with Riyadh.

UNSW researchers intend to work with the Royal Commission of Riyadh to roll out the heat mitigation plan for the city, which would be the largest of its kind in the world. 

“Once implemented at the city scale, these advanced heat mitigation technologies will deliver important health, sustainability and economic outcomes for the city for years to come,” says Santamouris. 

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