Australia's first ever national forum on Cooling Cities to tackle the Urban Heat Island effect (UHI) is being held this Friday, August 4, 2017 in Sydney.

UHI is where cities absorb and produce more heat than the surrounding countryside - it is a major contributor to city temperature spikes during very hot weather but evidence-based solutions are available to mitigate UHI through strategy, design, technology and use of nature.

The Forum, which will be attended by up to 100 key urban planning decision makers and experts, will be an opportunity to launch of the first Guide to Urban Cooling Strategies, including a special discussion paper on the topic.

The guide provides practical guidance for built environment professionals and regulatory agencies seeking to optimise development projects to moderate urban microclimates and mitigate urban heat island effects in major urban centres across a range of climates in Australia.

There will also be an update on a recently commenced project developing an Urban Heat Island Mitigation Decision Support Tool and a series of panel discussions to draw out present and future policy directions, industry perspectives and the latest international and national evidence for mitigation and planning.

The Forum will bring together local and global evidence on how to create urban cooling and strategies for mitigation.

It will also explore policies and regulations for all levels of government, show technologies and techniques for mitigation such as water and cooling technologies.

The official guide, which is designed to keep city dwellers cooler during hot weather by helping town planners, regulatory agencies, architects and developers mitigate urban heat islands and microclimates that cities create, was launched today by the CRC for Low Carbon Living (CRCLCL).

UNSW’s Dr Paul Osmond and CRLCL project leader, who led the team that compiled the Guide to Urban Cooling Strategies said it covered different climate zones that define cities across Australia.

“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,” he said.

“The importance of design to embrace 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.

“All these elements have an effect on urban temperatures. For example, radiant temperatures in urban parks with sufficient irrigation can be 2-4°C cooler compared with adjacent unvegetated or built-up areas, while air temperature reduction may be up to 2°C according to a park’s extent and the proportion of trees. This is is known as the park cool island effect,” explained Dr Osmond.

“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. A streetscape with heavy tree canopy can enjoy up to 15°C cooler surfaces and 1.5°C cooler air temperature compared with a street with no tree canopy and shade,” he said.

Three dimensions to contexualise the effectiveness of urban cooling strategies are used in the Guide: urban form, climate type and the nature of intervention. This matrix provides the Guide’s framework in terms of process (methods) and product (the design outcomes).

Dr Osmond explained that urban climates are ultimately created from a balance between the heat of the sun and heat lost from walls, roofs and ground; by heat exchange via air movement between ground, buildings and atmosphere; and by heat generation within the city itself, for example from motor transport.

“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. Studies across the world’s major cities show that a systematic higher average temperature of 2°C to 12°C exists in highly-urbanised areas compared with their rural surroundings,” Dr Osmond said.

CRCLCL CEO, Professor Deo 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,” he said.

“I believe the Guide to Urban Cooling Strategies should be read by all those involved in creating built environments so they can plan and design for the future, to ensure generations to come will be living in cities that minimise the effects of climate change, particularly when extreme heat is an outcome.”

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