A significant proportion of the total energy produced in Hong Kong is consumed by the building stocks, which account for nearly half of the total energy consumption. Due to expanding economy and substantial improvement in living standards over the past decade, the demand of electricity generation has remarkably increased. This rising trend of energy use will inevitably lead to increasing environmental problems. In this respect, a comprehensive set of codes of practice for energy efficiency in building services installation were drawn up by Energy Efficiency Office (EEO) in 1998 in Hong Kong. The codes represent a performance-based approach, which set maximum allowable energy consumption levels for various installations with statements of requirements and evaluation methods. This work evaluates the codes and their improvements on our environment by considering the energy saving, reduction of fuel use and pollutants emission from the power plants if the building energy code programmes become statutory. A group of pilot buildings selected from the commercial sector is used in an evaluation study. In particular, the potential reduction of greenhouse gases emission to the environment has been predicted for the justification of the usefulness of the energy codes. It is found that the application of building energy codes on these buildings has achieved a substantial reduction of energy consumption and an accompanied reduction of greenhouse gas emission. A simple benefit-cost analysis is also performed to evaluate the economics behind the codes and the results fully justify its enactment. (c) 2004 Elsevier B.V. All rights reserved.