Infrastructure Engineering - Research Publications
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ItemEffects of substrate depth and native plants on green roof thermal performance in South-East Australia(IOP Publishing, 2020-11-20)Three experimental green roofs in Melbourne with depth of 100, 150 and 300 mm have been assessed to quantify their thermal performance. To evaluate the benefit of substrate depth, temperature was recorded every 50 mm along a vertical profile. Green roofs consisted of scoria substrate and a mix of three species of plants: Lomandra longifolia, Dianella dmixta and Stypandra glauca. Statistical analyses applying the hierarchical partitioning technique showed that solar radiation is the main driver affecting the green roof surface temperature, air temperature has strong correlations with the variations of the temperatures recorded below the surface, while moisture content has the least influence. Temperature profiles of the green roof show that the first 50 mm do reduce the heat flowing through the green roof substrate regardless the total green roof substrate depth. Differences in thermal performance arise at deeper points, where thicker green roofs are able to delay the change of substrate temperatures. Similar effects were found for the heat fluxes measured at the interface between the green roof and building roof. These results confirmed that green roofs may be used as a sustainable passive technology to reduce building energy consumptions for South-East Australia climate.
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ItemNo Preview AvailableTrees provide energy saving benefits to adjacent buildings for a small water cost(Australian Sustainable Cities and Regions Network, 2011)
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ItemGreen roofs in Australia: review of thermal performance and associated policy development(The Architectural Science Association, 2016-12)In Australia, there is an increasing interest in using extensive green roofs to make buildings more sustainable and provide a number of social, ecological, aesthetic and thermal benefits to cities. The potential of green roofs to reduce building energy consumption has been extensively studied overseas in a variety of different climates. However, in Australia the green roof industry is relatively new. There is still very little information on the thermal properties of Australian green roofs and their performance. Further, as a relatively new industry, there is a general lack of specific policies and initiatives to promote green roofs. In this paper, we briefly review the research investigating green roof thermal performance in various climates and analyse policies and actions that have been implemented internationally to foster green roofs with an emphasis on their thermal performance. The results showed that most policies were focused on ecological benefits, such as stormwater runoff reduction, rather than thermal benefits. Many green roof policies had difficulty interpreting the thermal performance of green roofs, because of the dynamic nature of green roof R-values. In this study, the effectiveness of overseas green roof policy is discussed and recommendations how they could be adapted for Australian cities are provided.
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ItemEffects of design and operating parameters on green roof thermal performance in Melbourne(ZEMCH, 2016)The growing interest in extensive green roofs prompts more refined studies on green roof design and operation. To assist in the design, installation and operation of green roofs, the effects of design and operating parameters on green roof thermal performance need to be fully understood. The effects of two design parameters: substrate thickness (ST), conductivity of dry soil (CDS) and four operating parameters: leaf area index (LAI), leaf reflectivity (LR), stomatal resistance (SR), moisture content (MC) were investigated using the green roof model developed by Sailor in 2008. The sensitivity analysis revealed that among the operating parameters, LAI has the largest effects on thermal performance. On the other hand, between the two design parameters CDS is more influential than ST. An experimental investigation in Melbourne of non-vegetated green roofs with three substrate thicknesses (10 cm, 15 cm and 20 cm) and on a bare conventional roof was employed to isolate the effect of plants and enable better understanding of heat transfer mechanisms involved. In contrast with the sensitivity analysis, the experimental results for summer and winter showed the importance of the ST in reducing the substrate temperature and heat flux across the green roof. They also showed how the green roof substrate alone reduces the heat flux compared to the conventional roof. Finally, the thermal performance of sparsely vegetated green roofs in summer revealed a contribution to cooling effect of plants.