An Evaluation of the Potential Energy Benefits of Installing Green Roofs in Hong Kong

Green roofs help mitigate the urban heat island effect, increase available green space, and reduce energy consumption of buildings. This thesis estimates potential energy benefits of installing green roofs on buildings in Hong Kong. EnergyPlus, a building energy simulation program, is used to model an extensive green roof installed on a two-story building in downtown Hong Kong. Indoor and outdoor temperature data were collected from the green roof. Model calibration is performed using monitoring data, meeting the set acceptable margin of error of ± 20%. Air conditioning usage from April to September is approximately 232 kWh less in the room under the green roof that for the original roof showing that green roofs can reduce heat flux from the roof into buildings. Compared to other energy saving technologies, the cool roof provides a savings of 184 kWh over the green roof, translating to a $55 annual reduction in energy costs.