A multi-criteria decision analysis model for delivering low carbon office buildings in Hong Kong

Abstract

Buildings worldwide account for over a third of carbon emissions, which have a tremendous impact on climate changes. Meanwhile, their contribution in Hong Kong is much higher, being up to 60%. Therefore, low carbon building (LCB) has been regarded as an effective approach to reducing carbon emissions worldwide especially in Hong Kong. There have also emerged a wide range of measures for achieving LCBs.

However, the effective utilization of LCB measures faces the challenge of identifying and selecting those proven to be environmentally, technically, financially and socially sustainable in the long term. This challenge is particularly significant at the design stage of LCBs due to the limited or unknown design information. These problems may be well addressed by the multi-criteria decision analysis (MCDA). However, the current body of knowledge of LCB has two limitations. Firstly, most of previous research did not categorize the possible LCB measures from a systematic perspective, which results in fragmented evaluation. Secondly, the MCDA method still has not been widely used for solving the decision-making problems regarding LCB thus lacking the supportive information for its effective utilization.

In addressing these limitations, this research aims to develop a MCDA model for the selection of appropriate LCB measures for office buildings in Hong Kong. Office buildings are a great representative of commercial buildings which contribute more than 60% of the carbon emissions of the building sector in Hong Kong. This research was carried out through the combination of a critical literature review, a questionnaire survey, a project case study and personal interviews. The literature review was focused on examining the frameworks for identifying LCB measures and selecting decision criteria. A questionnaire survey was carried out with 355 BEAM Professionals in Hong Kong, which expanded and verified the results from the literature review. The case study was conducted with an office building project using building performance simulation (BPS) for further investigation. The interviews were semi-structured in nature, carried out with 10 construction experts in Hong Kong.

Through the research 10 LCB measures and 6 decision criteria for the LCB measure selection were identified, which were mostly used or considered for office buildings in Hong Kong. The developed MCDA model contains 5 modules that help to structure the decision-making process. The relative importance of the 10 LCB measures was obtained by a general implementation with proper weighting method and MCDA method. The results demonstrate the importance of lighting and building envelope for low carbon office building design and the need for accurate data for informed decision-making. Software eQuest was used for evaluating the carbon reductions in the case study building, and Software Visual PROMETHEE was adopted for selecting the best alternative among the LCB measures investigated. The developed MCDA model should support design decision-making for selecting appropriate LCB measures for office building projects. Despite the adopted multi-criteria decision-making, building energy regulations and government incentives in favour of building carbon reductions were mostly expected for delivering LCBs in Hong Kong.