Are green buildings in Hong Kong energy efficient? : a case study of the Chinese University of Hong Kong

Abstract

Following the adoption of the Paris Agreement at the 21st session of the Conference of the Parties (COP21) to the United Nations Framework Convention on Climate Change (UNFCCC) on 12 December 2015. Many countries or local governments including Hong Kong have already set certain sustainability targets in response to the hot topic of climate change. Hong Kong government set an ambitious energy saving target which was to achieve energy intensity reduction by 40% by 2025 using 2005 as the base year in the energy saving plan. One of the main measures is to commit all new major government buildings and new public housing developments to achieve BEAM Plus Gold or better rating that may improve the buildings’ energy efficiency for reducing greenhouse gas emissions. Therefore, this paper is trying to find out the gap of the energy performance between the Hong Kong certified green buildings and traditional buildings which may give an insight about the direction of the Hong Kong energy saving plan.

The Chinese University of Hong Kong (CUHK) has been awarded the highest number in certified green buildings among tertiary institutions in Hong Kong. Taking this university as a case study is more persuasive. About the study methodology, the weather-normalized Energy Use Intensity (EUI) in terms of floor area of individual building has been used as an unit of building energy performance for comparison. Internal benchmarking among the buildings within campus and public benchmarking with Energy Utilization Indexes prepared by the Electrical and Mechanical Services Department (EMSD) were carried out. This study covers four building categories including student hostel, library, teaching building and laboratory building.

In both internal and public benchmarking exercises, the certified green buildings in CUHK campus have no advantage in building energy performance. On the contrary, except library category, the worst building performance in other three categories are certified green buildings. From the study, it is found that the existing green building assessment tool cannot safeguard the building energy performance. Also the green building with higher grade does not represent that they have better energy performance than the one with lower grade.

The findings show that the tool does not help to correct the existing malpractice related to air-conditioning system design and operation. Selection of air-conditioning systems and the efficiency of the part-load operation of a central system are still the crucial problems affect the building energy performance. Another potential problem is the requirements of indoor environmental quality. To maintain such high standard of Indoor Air Quality (IAQ) in Hong Kong would indirectly create higher energy loading demand on air-conditioning system.

Coincidently, all the green buildings in CUHK are assessed by the tool for new buildings. It reveals that the problems of the imbalanced effort on implementation of the tool for existing buildings and the policy inclination for new green buildings occur. These findings have significant implication that the existing green building scheme and policy cannot contribute to the Hong Kong’s long-term sustainability target effectively by lowering the energy performance of buildings. A holistic approach in improving energy performance for both new and existing buildings is necessary, especially for the existing ones which dominate the energy consumption in Hong Kong. Otherwise, all the beautiful green buildings in Hong Kong can only demonstrate a good model for education purpose.