Urban tree planting is widely recognised as a means of adapting our cities to increasing temperatures and more frequent, intense and longer lasting heatwave events. Many local governments in Australia are implementing strategies to increase urban tree cover in the public domain. While this is entirely appropriate, research shows that in many cities, the majority of tree cover is found in private gardens. There is very little known about how effective private tree cover is for adaptation to climate change.

In this presentation, we describe the findings of a project which quantified the potential benefits of tree shade for reducing heat-related health risk and the cooling energy requirements of housing in Western Sydney. Results were generated using the numerical building simulation software AccuRate for a reference climate (2000) and projected future climates (2030 and 2070) using different tree shade scenarios to test the influence of tree size and location, canopy porosity, and leaf-fall habit.

Under the reference climate scenario, tree shade to the east and west of the house saved energy by allowing solar access in winter while blocking solar heat gain in summer, whereas trees to the north increased heating energy costs. This seasonal trade-off is diminished with climate change as the requirement for cooling energy increases, and by 2070, trees to the north further reduced cooling costs, challenging conventional design practice regarding solar access. Irrespective of the energy savings, under nearly all tree shade scenarios, the heat-related health risk to occupants is reduced.