Energy and economic performance of green roof system under future climatic conditions in Hong Kong

In this study, an experimental setup of a green roof system was established on the rooftop of a commercial building for computer model validation. Then a generic office building constructed with green roof was modeled using EnergyPlus and its energy performance was evaluated under different future climatic conditions over three future periods (2011-2030, 2046-2065 and 2080-2099) and two emission scenarios (SRA1B and SRB1). The findings show that a combination of thicker soil layer, lower plant height and higher value of leaf area index (IAI) can provide a better thermal insulation effect in a green roof system. The results reveal that a building case with soil thickness of 0.4 m, plant height of 0.05 m and LAI of 5 can maintain the year-round A/C energy consumption no more or less than the current level, ranging from -2.4% to -10%, under the future climatic conditions (2011-2030 and 2046-2065, for both emission scenarios). Economic evaluation on the application of green roof was also conducted. Taking into account the replacement cost of a conventional bare roof, the cost payback period is about 10 years. The application of green roof system can act as a potential measure to cope with the impact of climate change. (C) 2013 Elsevier B.V. All rights reserved.