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Purpose: The purpose of this paper is to present a tri-optimization approach to optimize design solutions regarding the building shape and envelope properties considering their implications on thermal comfort, visual comfort and building energy consumption (EN). The optimization approach has been applied to obtain the optimal design solutions in five typical cities across all climatic regions of China. Design/methodology/approach: The method comprises a tri-optimization process with nine main steps to optimize the three objectives (thermal comfort, visual comfort and building EN). The design variables considered are four types of building shape (pyramid, rectangular, cylindrical and dome shape) and different envelope properties (insulation thickness [INS] of external walls/roof, window type [WT] and window-to-envelop surface area ratio [WESR]). The optimization is performed by using the Taguchi and constraint limit method. Findings: The results show that the optimal design solutions for all climatic regions favor cylindrical shape and triple-layer low-E glazing window. The highest insulation level of 150 mm is preferred in three climatic regions, and the INS of 90 mm is preferred in the other two climate regions. In total, 10% WESR is preferred in all climatic regions, except the mild region. When the constraint limit of lighting intensity requirement by Leadership in Energy and Environmental Design (LEED) is applied, the rectangular shape building is the optimal solution for those with 10% WESR. Research limitations/implications: The method proposed in the paper is innovative in that it optimizes three different objectives simultaneously in building design with better accuracy and calculation speed. Practical implications: Building designers can easily follow the proposed design guide in their practice which effectively bridges the gap between theory and practice. The optimal design solutions can provide a more comfortable living environment and yet less EN, which can help achieve the sustainability requirement of green buildings. Social implications: The solutions presented in the paper can serve as a useful guide for practical building designers which creates economic and commercial impact. In addition, the theory and practical examples of the study can be used by building regulators to improve the energy-efficient building design standard in China. Originality/value: The research is the first attempt that adopts tri-optimization approach to generate the optimal solutions for building shape and envelope design. The tri-optimization approach can be used by building designers to generate satisfactory design solutions from the architectural viewpoint and meanwhile to find combinations of the building shape and envelope properties that lead to design solutions with optimal building performance. [ABSTRACT FROM AUTHOR]

Purpose - The recession in the late 1990s in Hong Kong has triggered many commercial building owners to cut operation and maintenance (O&M) cost via outsourcing. The purpose of this paper is to investigate the dominant expenditure on O&M service and examine the relation between extent of outsourcing and rental income of the buildings. Design/methodology/approach - Experienced O&M practitioners were interviewed to collect both quantitative and qualitative data of the commercial buildings they looked after. The in-house and outsourced O&M costs, air-conditioning energy costs, rental incomes, and management and air-conditioning fees for the buildings were analysed. Findings - The total air-conditioning O&M cost is the principal cost item, with the energy cost being the dominant element. The analysis reveals that the extent of outsourcing bore little correlation with the air-conditioning O&M cost and the rental income. Research limitations/implications - Further work may take a similar approach to identify the extent and effect of outsourcing other kinds of services that underpin the core business of an organisation. Practical implications - Varying the extent of outsourcing O&M service was found to be unpromising for enhancing rental performance or cutting O&M expenditure. This is an important point that the building managers should address when considering whether to go for outsourcing. Originality/value - The findings imply that in the building O&M service industry, it would be more economical to outsource or undertake in-house the vast majority of O&M work. The focus for cost minimization should be to improve building energy performance rather than reducing labour resources through outsourcing. [ABSTRACT FROM AUTHOR]

Purpose - To explain the recent emergence of the trend of outsourcing for building services operation and maintenance (O&M) work for commercial buildings in Hong Kong and to predict its future development. Design/methodology/approach - Based on economic theories, the authors' understanding of buildings and building services O&M in Hong Kong and information regarding property, companies and manpower statistics, the increasing use of outsourcing is explained with a prediction of its implications for industry stakeholders and future trends. Findings - Reports the common operation and maintenance organization for small, medium and large commercial buildings and explains the relation between outsourcing and the recent economic downturn and sharp cuts in O&M expenditure. Analyses the factors influencing O&M costs and predicts that the trend of outsourcing will continue if contractors keep on upgrading their knowledge and skills to provide quality services more economically than the in-house workforce. Research limitations/implications - The explanation and prediction rely greatly on economic theories and the authors' knowledge and observations from industry, yet the reason for outsourcing and the factors influencing O&M costs are unveiled. Practical implications - The findings have exposed implications for building owners and O&M practitioners as a result of the outsourcing trend, on top of establishing a rigid framework for future practical research in the area. Originality/value - This paper explains the prime motive for outsourcing building services O&M work for commercial buildings, predicts future trends and reveals the implications for stakeholders in the O&M industry in Hong Kong. [ABSTRACT FROM AUTHOR]