Assessment of climate change impact on building energy use and mitigation measures in subtropical climates

Likely increase in energy use in air-conditioned office buildings due to climate change in subtropical Hong Kong was estimated for two emissions scenarios. Towards the end of the 21st century (i.e. 2091–2100), the average annual building energy use would be 6.6% and 8.1% more than that in 1979–2008 for low and medium forcing, respectively. Potential mitigation measures concerning the building envelope, internal condition, lighting load density (LLD) and chiller plant were considered. Thermal insulation to the external wall would not be effective to mitigate the expected increase in building energy use due to climate change. Controlling the amount of solar heat gain through the window would be a better option. Lowering the current LLD of 15W/m2 to about 13W/m2 would result in substantial energy savings because of the reduction in electricity consumption for both electric lighting and air-conditioning. As for the chiller plant, the coefficient of performance (COP) should be improved from the current minimum requirement of 4.7 to at least 5.5 to alleviate the impact of climate change. Raising the summer set point temperature (SST) to 25.5°C or higher would have high energy saving and hence mitigation potential, which could be readily applied to both new and existing buildings.