Rooftop greenery systems in subtropical climates for environmental sustainability : a review

Green roofs can offer a sustainable green surface by improving urban climate, minimizing heat island effects and simultaneously protecting biodiversity. It can protect the roofing membrane from exposure to ultra violet radiation and hail damage. Green roof can reduce energy demand on space conditioning, and hence greenhouse gas emissions. It is not a cooling device rather it works as an improved insulation. Plants absorb a significant portion of solar energy through biological functions and the remaining solar radiation that would affect the internal temperature of the building is much less than that of a bare roof. In comparison with other developed countries, Australia has been slow to adopt green roofs and no solid platform has yet been developed in Australia. Due to the significant differences in climate and available substrates and plants, European and American experimental data and technology cannot be used locally (in Australia) to implementing rooftop greenery systems. However there are some scattered examples of usage of green roofs in Australia and majority of green roofs are constructed for decorative purposes. This paper presents a review and discusses the impact of green roofs on thermal transfer value, building energy consumption and environmental sustainability in subtropical climate.