Central to the global warming problem are the continuously increasing emissions of greenhouse gases (or carbon emissions), especially those associated with the operation of buildings. Funded by the Research Grants Council of the Hong Kong Government (Project No. PolyU 152095/15E), a multi-stage study that aims to understand how to achieve an optimum balance between the operating resources and the carbon footprints of existing commercial buildings in Hong Kong has been conducted. The Principal Investigator of the study, Dr Joseph Lai, will present in this seminar the works carried out for the study and the findings obtained, such as the conceptual research model for the study, method used to quantify carbon emissions, sources and amounts of operating resources and carbon emissions of the buildings studied, and cost effectiveness of implementing retrofits to improve building environmental performance.