Despicable Urban Places: Hot Car Parks

Abstract

Cities are warmer than surrounding non-urban areas. Climate models predict that metropolitan centres will become even warmer due to the dual impacts of global warming and densification. However, the outer fringe zones of metropolitan centres will also become warmer as a consequence of urban expansion that requires replacing green and open spaces like pastures or bushland with grey infrastructure such as roads and buildings. Limiting the warming effect of urban expansion is possible. It requires dedicated heat-responsive planning and design strategies being applied systematically and at scale. But where should planners and developers start to effectively reduce urban heat? At-grade car parks are an ideal starting point. They represent the ‘low-hanging fruit’ for urban cooling efforts. While unavoidable today and in the near future, at-grade car parks are predominately unshaded; made from black, heat-retaining asphalt; widespread and fairly uniform; and often large in size. Changes to current designs of at-grade car parks can therefore have a big impact. A number of strategies to effectively reduce surface heat of car parks are commercially available. Cooling car parks not only addresses their status as local heat islands, but it also leads to lower ambient air temperatures in downwind environments. This report documents:   Microclimates across eight car parks and reference sites covered by vegetation. Measurements of surface and air temperatures related to a range of car park surface materials. The cooling effect of shade in car parks. Current design guidelines and policies in Australia related to car parks. Alternative design solutions for cooler car parks. The empirical data and policy analysis are used to develop a set of recommendations for urban heat mitigation that can be applied to new and existing car parks. Because of the common nature of at-grade car parks around the world, the proposed cooling techniques can be applied globally, irrespective of the fact that the underlying case studies and data originated from Sydney.