Federal policy sorely lacking on cooling cities

Federal policy on the urban island heat island effect is a sorely missing piece of the puzzle to cool our cities, according to the CRC for Low Carbon Living chief executive Professor Deo Prasad.

Professor Prasad joined experts at last week’s Cooling Cities National Forum in Sydney to debate how to tackle the growing urban heat island effect problem, and to launch a new national guide on urban cooling strategies.

“Most of the action is at the local government level,” he said.

State governments have supported local action to varying degrees, but while the federal government had made some talk about urban forestry when Greg Hunt was environment minister, there hasn’t been much talk since.

Professor Prasad would like to see the federal government’s City Deal projects take mitigating urban heat into consideration.

The Cool Cities forum brought together over 100 attendees from urban planning, academia, development and consulting to discuss global and local methods, and examples of creating urban cooling to mitigate urban heat.

“The forum was about putting on the table what evidence there is about urban warming, and the different strategies that work or don’t.”

It looked particularly at the role of vegetation, water, cooling technologies and the scale of impact each potential strategy has.

New research by the CRC was also presented that examined the impact of urban heat on people in Western Sydney in terms of comfort, wellbeing, health and morbidity, with Professor Prasad saying there was a “significant” temperature difference between eastern and western Sydney.

Launch of Guide to Urban Cooling Strategies

The event also saw the launch of a new national guide on urban cooling.

The Guide On Urban Cooling Strategies aims to assist landscape architects, urban designers, planners, local authorities, government agencies and developers in mitigating urban heat islands, by setting out the pros and cons of various strategies and giving specific advice for major Australian cities across the key climate zones.

“The range of urban landscapes that the guide covers include dense inner cities, middle ring and outer suburbs, with a focus on design intervention, including streetscapes, plazas, squares and malls,” lead author and sustainable development director at UNSW Built Environment Dr Paul Osmond said.

“The importance of design which embraces vegetation cover, particularly tree canopy; the use of shade to minimise heat; and the orientation of these elements are also key to cooling. Interventions may be active, such as misting systems and awnings, or passive, like street trees, green roofs, water bodies, cool roofs and facades.”

Research has shown that radiant temperatures in urban parks with sufficient irrigation can be two to four degrees cooler than adjacent built-up or unvegetated areas. Air temperatures can be up to two degrees cooler, according to the park’s area and extent of tree coverage.

“This is known as the park cool island effect,” Dr Osmond said. 

“The guide also highlights the fact that street trees contribute to radiant and air temperature reduction by evapotranspiration and shading over buildings and street surfaces.”

The guide takes an integrated approach to urban climates.

Dr Osmond said urban climates were created by the balance between the heat of the sun and heat lost from walls, roofs and ground; heat exchange via air movement between ground, buildings and atmosphere; and heat generation within the city itself, for example from motor transport and airconditioning use.

“Global climate change and the urban heat island phenomenon – where cities absorb and release more heat than the surrounding countryside – carry growing potential to make urban life at particular times and places an exercise in low-grade misery,” he said.

Collaborators on the guide included experts from HASSELL, AECOM, Arup and the NSW Office of Environment and Heritage.

Professor Prasad said the guide was also a major milestone in the CRCLCL’s work as it brings together data from a three-year urban microclimates project it has funded.

“This publication is unique, as it not only draws on our painstaking three-year research along with global research, it cross-references to our Microclimate and Urban Heat Island Decision-Support Tool project and benefits from relevant research at the CRC for Water Sensitive Cities,” Professor Prasad said.

He said the tool would allow people during the planning stages to compare what options would work best for mitigation potential in specific climate zones. It is expected to go live later this year.

Roger Swinburne, technical director at AECOM, said the consultancy could “see the benefits of bringing academic rigour to the way we plan our public domain and how it can influence the way cities deliver open space”.

• Download the Guide to Urban Cooling Strategies