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Urban Heat Island Mitigation Performance Index

Solution Overview

The Urban Heat Island Mitigation Performance Index represents a decision-support framework developed to assist governments in establishing performance targets for planning control across Sydney and regional New South Wales.[1][2] This approach was carried out by UNSW Sydney and Swinburne University in collaboration with government and industry partners from January 2017 to December 2018, with funding from the CRC for Low Carbon Living.[1][2] The system indicates impact on street level temperature, health and mortality, and precinct level energy consumption to inform urban policy, development assessment and planning practices.[1][2][4]

Technical Components

The initiative comprises a web-based decision-support tool accessible at uhimitigationindex.fbe.unsw.edu.au, alongside a Microclimate and Urban Heat Island Mitigation Decision Support Tool with restricted access.[1][2] Login credentials for the restricted tool can be requested from UHI-Index@unsw.edu.au.[2] The system models various mitigation strategies including cool roofs, cool pavement, greenery with water irrigation, water-misting and outdoor shading to assess their combined effects on urban temperatures.[3] Modelling capabilities evaluate subdivision scenarios to analyze how reducing lot sizes while increasing building density affects outdoor air and surface temperatures.[3]

Implementation Details

Government and Industry Partners and Steering Committee for the UHI-DS project comprised: City of Sydney, Greater Sydney Commission, OEH, Landcom, Parramatta City Council, Campbelltown City Council, WSROC, SSROC, Sydney Water, Inner West Council, Waverley Council, NSW Spatial Services, Stockland, BlueScope Steel, AECOM, PSMA, UNSW and Swinburne University.[1] The project was funded by CRC for Low Carbon Living and completed between January 2017 and December 2018.[1][2] Regional applications extended beyond Sydney to include analysis of areas in Maitland and Dubbo.[3] In Southlakes, Dubbo, various subdivision scenarios were analyzed to demonstrate how implementing a combination of mitigation strategies can effectively reduce the heat effects associated with increased building density.[3]

Benefits and Impacts

Modelling showed that the use of cool roofs, cool pavement, greenery with water irrigation, water-misting and outdoor shading could reduce air temperature by 1.6°C in the areas studied in Maitland and 2°C in the areas looked at in Dubbo.[3] Surface temperature reductions exceeded 10°C in each location analyzed.[3] Results from Southlakes indicate that while reducing lot sizes while increasing building density leads to increased outdoor air and surface temperatures, implementing a combination of mitigation strategies can effectively reduce the heat effects associated with increased building density.[3]

Climate Adaptation Relevance

This approach addresses urban heat island effects that create significant temperature disparities across metropolitan Sydney. Because of the intense development of the UHI in Sydney, Cooling Degree Days in Western Sydney are about three times higher than in the Eastern coastal zone.[2] The performance index enables governments to establish planning controls that mitigate these temperature differentials and their associated health and energy consumption impacts.[1][2]

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