In the tropics, the earth surface receives abundant solar radiation throughout the year contributing significantly to building heat gain and, thus, cooling demand. An effective method that can curb the heat gains through opaque roof surfaces could provide significant energy savings. This study investigates and compares the effectiveness of various passive cooling techniques including cool roof, green roof and thermal insulation for reducing the heat gain through a flat concrete roof in tropical climate. Computational simulations are performed on a single storey building with 100-mm-thick concrete flat roof. The simulation model is calibrated by measurements conducted in the real building that the simulations modelled after. Simulation results show that a new cool roof reduces net annual heat gain through the roof by about 89-90%, a green roof reduces by about 32-41% and thermal insulation (50-mm-thick polystyrene) reduces by about 62-72%. It means that the annual net heat gain reduction provided by cool roof is the highest among the three passive cooling technologies in the tropical climate. Cool roof enhances heat release from the building whereas green roof and thermal insulation impede building heat release during night time.
Keywords: Cool roof, green roof, thermal insulation, tropical climate, building energy