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Natural ventilation and the type of window used are closely related. Many works have already been done on identifying the window types that can enhance ventilation performance in residential buildings. However, window performance has been investigated either independently, without considering the interactive effects of other apertures (relative positions of windows and window orientations) or it has been examined based on very limited wind data sets. To fill this research gap, this study aims to evaluate the influence of window types on indoor ventilation performance of residential units in Hong Kong, taking into account the interactive effect and based on representative wind data sets. Air change per hour (ACH) was used to quantify natural ventilation. In this study, site measurement was conducted at a carefully selected residential unit to provide data for validation of the Computational Fluid Dynamics (CFD) settings. The validated settings were used for further CFD simulations. The Central Composite Design method and the Squeeze Theorem were used to determine the representative wind data sets. The Response Surface Regression method was used to develop a mathematical model for quantifying the interactive influence of different apertures on indoor ventilation and to enable quick estimation of ACH. The results lead to the conclusion that for all apertures, side hung (SH) window is the most effective design, followed in descending order by top hung (TH) window and sliding (SLD) window. The maximum achievable ACH for SH and TH windows were 124% and 97% higher than the SLD window. It was also found that if windows can be located only on the same side of a residential unit, SH windows and south facing TH windows should be preferred.

Sleep is a dominant part of our daily lives. People often have sleeping habits. Sleeping habit is referred as the preferred bedding system (type of bedding and sleepwear) and thermal environment. Thermal environment and cooling energy use are closely related. Many works have been done on sleep quality, sleeping habits, and the associated cooling energy use. However, it is noted that they are either separately or pairwise investigated. No investigations to date have been done to investigate their interactive effect. This study serves as a pilot study to fill the research gaps in investigating the interactive effect of sleep quality, sleeping habits and cooling energy use. Based on the use of three bedding systems and four temperature settings, 12 sleeping tests, each refers to one sleeping habit, were performed simultaneously in eight subjects. Sleepbot was employed to quantity sleep quality. Upon ascertaining the best sleep quality for different bedding systems, hour-by-hour energy simulations using EnergyPlus were conducted. It was found that for the use of light bedding systems, the associated drop in energy use would be 78.3% and 37.8% for female and male subjects respectively. Two prediction models, one relating energy use with thermal environment, and the other relating sleep quality with sleeping habit, have been established. The models can help quickly determine the tradeoff amongst sleep quality, sleeping habit and energy use.

It has been a common practice to place room air-conditioners (RACs) at overhead level for cooling of residential environments because this offers better air distribution performance and thus thermal comfort. However, now reversible RACs are gaining ground and they comprise both cooling and heating modes. Whether the same practice of locating RACs at overhead level should continue for reversible RACs has never been investigated. This study is the first ever attempt to identify the optimum positioning (position and level) for installation of reversible RACs in a representative bedroom. Computational Fluid Dynamics (CFD) and EnergyPlus simulations were integrated for the purpose and experiments were conducted in an environmental chamber to provide data for validation of the CFD settings. EnergyPlus simulations were used to determine the hour-by-hour cooling and heating demands based upon realistic operating and probable equipment characteristics. The probable equipment characteristics were ascertained by an extensive market survey and Monte Carlo analysis. The hour-by-hour cooling and heating demands were analysed by Central Composite Design method and the Squeeze Theorem for the formulation of the representative cooling and heating data sets for further CFD simulations. Further CFD simulations provide an accurate prediction of air temperatures and velocities for different installation positioning for thermal comfort analysis. Revised air diffusion performance indices (ADPIs) were developed to facilitate thermal comfort analyses for cooling and heating modes. It was found that slightly higher ADPIs can be obtained when the reversible RAC is installed at high level and on the longer side of the bedroom.

Natural ventilation performance of a residential dwelling is affected by a combination of internal and external factors. External factors are often subject to constraints beyond the control of site planners and architects. Internal factors include the openings configuration, which site planners and architects are free to design the way they deem proper. However, little information is available in this regard. In this study, a case study was conducted by tracer-gas measurements at a carefully selected residential unit for Computational Fluid Dynamics (CFD) model validation. A hypothetical residential unit was formulated to represent the characteristics of typical residential units in Hong Kong. CFD simulations were performed based on the hypothetical unit to evaluate the influence of different openings configurations on natural ventilation performance using the mean age of air. Openings configuration is defined by many parameters. Among the three studied parameters, evaluation results indicate that natural ventilation performance of residential units was most affected by the relative position of the two window openings groups (i.e. bedroom windows and living room windows), followed by building orientation and doors positions. It was found that better natural ventilation performance could be achieved when the two openings groups were positioned in opposite directions or perpendicular to each other. The combined effect of the three parameters was evaluated. It was found that varying two parameters at the same time offered positive improvements in natural ventilation performance, but varying all three parameters did not result in any improvement because of the counter-effects of changes in doors positions.

The feasibility of locating the air-conditioners at low level (FAC unit) for residential use has been ascertained in previous studies by the authors. In order to optimize the design of the unit for maximum thermal comfort, an FAC unit configured to two different angles of deflection and two installed positions (altogether 4 scenarios) was set-up in a 13 m2 bedroom-like chamber for experimental studies. In the experiments, the layout of the chamber was determined by questionnaire surveys, and the characteristics of heat source were determined by heat transfer simulations and cluster analysis. The local air speeds and temperatures at 4 different levels of 8 positions were monitored for the calculation of air diffusion performance index (ADPI) and draft risk. The energy performance was determined based upon the monitored cooling outputs and power consumptions. Using the measured air temperatures and velocities as boundary conditions, three-dimensional computational fluid dynamic (CFD) simulations were performed using AIRPAK to examine the vertical temperature distribution, draft discomfort and ventilation effectiveness. It was concluded that the FAC unit with an angle of deflection at 45° and with a finished level of 1.1 m performs better than the unit with other configurations. No thermal stratification and draft discomfort were observed. Further, by using parametric studies, the influences of space cooling loads, supply air velocities, and jet areas were investigated with 24 CFD cases. Based on the simulation results, for a satisfactory ADPI for the use of FAC unit, the optimum supply air velocity range was identified as 2.2 m/s–3 m/s, whilst the Ar numbers were between 0.033 and 0.243.

The Hong Kong Building Environmental Assessment Method (HK-BEAM), Building Research Establishment Environmental Assessment Method (BREEAM) and LEED were formally launched in the 1990's. How well the certified and rated buildings compare with each other of an interest to building designers and policy makers. This paper describes how the baseline buildings, performance criteria and the credit scales of the three schemes compare with each other. By statistical analysis of the energy assessment results of 60 HK-BEAM certified buildings and the available data for BREEAM and LEED, it seeks to ascertained of buildings scoring excellent energy performance under different schemes belong to the top 5% in the market. Through this exercise, a systematic approach to benchmark the energy assessments across schemes has been established. With people nowadays paying greater attention to the environmental issues and the rapid development of the environmental schemes in various parts of the world, this study forms a good basis for future benchmarking of energy assessment schemes across nations.

In Hong Kong, there has been increasing public demand for developers to pay greater attention to the development of sustainable buildings. A creditable assessment scheme that provides targets and methods and recognition of the efforts that are made in this direction is considered to be an effective way to achieve the goal of construction sustainability. GBTool is by far the most comprehensive building environmental assessment framework and has been developed over the past 6 years through the efforts of 21 national teams. This study aims to address the customization of GBTool as a scheme to assist in the development of more sustainable buildings in Hong Kong. The general principle of triangulation is adopted in the customization process and the initiatives of the Hong Kong government and of voluntary bodies are reviewed. The gaps between the Hong Kong situation and the philosophy of GBTool are identified and a questionnaire survey and a series of in-depth interviews to elicit the attitudes of the parties involved toward the inclusion of additional issues into the customized scheme are conducted. The correlation of several major issues and the weightings across issues and criteria are identified. The results form a good basis for the development of a building sustainability assessment scheme for Hong Kong.

Economic principles have been applied to elicit the conditions under which there will be benefit to power companies in offering rebates to consumers to encourage them to adopt energy saving measures. The analysis also provides an answer to how rebate rate should be determined to maximise social benefit. However, the analysis of the rebate-based demand side management (DSM) programmes launched by the two power companies in Hong Kong in the year 2000 showed that the prerequisite conditions that would permit the power companies to derive benefits from the programmes were unlikely to exist. This suggests that use of this economic instrument for promoting energy efficiency requires governmental influence; it will not emerge solely as a commercial decision of the power companies in Hong Kong.

This paper reports a pioneering and quantitative approach being developed for assisting a large-scale high-rise residential building developer in Hong Kong in monitoring the competitiveness in the supply of fresh and flush water pumps to the building development projects. Integrated empirical pricing models based upon the hedonic price technique have been developed for the supply of both fresh and flush water pumps to the developer and the competitive sector. Our results revealed that the pricing levels charged to the developer were comparable to the competitive sector even though the quality standards of water pumps delivered were much lower. Upon close examination of the market structure, it was found that this was possibly due to the Limit Pricing Strategy being adopted by two leading suppliers in the developer's market as a result of relaxing the pre-qualification to standards below the industry norm. This finding should add to our understanding on the impact on the market competitiveness due to relaxation of pre-qualification requirements. Besides, measures of enhancing competitiveness in the supply market have also been discussed.

This paper reports an innovative, scientific and yet practicable approach developed in assisting a large-scale high-rise residential building developer in Hong Kong for monitoring the competitiveness in the switchboard supply to her development projects. In this study, a pricing indicator was developed for monitoring whether the pricing levels charged to developer had attained a competitive level. Our results revealed that the pricing level charged to the developed was far from competitive, and the high cost was contributed by inadequate competitiveness in the switchboard supply as a result of the practice of including only a limited number of suppliers on the pre-qualification list. By relaxing the pre-qualification requirements, the pricing level dropped to a very competitive level after two additional suppliers being included on the list.

A major strength of the voluntary building environmental assessment method is to encourage good environmental practice beyond the current industry practice. For a successful voluntary scheme, the credit scale must be attractive to investors and performance-based criteria should be used. However, most of the current schemes use a combination of prescriptive and performance-based criteria, and credits are allocated using subjective judgement, irrespective of cost and practical implications of attaining improved performances. This is pointed to the need to establish an incentive-crediting scheme, which is oriented towards performance-based scales having credits linked to cost and performance. In formulating the incentive-crediting scheme, the cost effectiveness of different energy-saving level in a base building is investigated under the premise that the investors would pursue a strategy in the most cost-effective manner. This paper presents a conceptual framework for policy makers to formulate an incentive-crediting scale for accrediting criteria within the greenhouse gas objectives of a building environmental assessment scheme in Hong Kong, aiming to attract participation of the profit-maximising investors. Establishment of an incentive-crediting scale starts from developing a carbon dioxide abatement curve for greenhouse gas emission. This is subsequently followed by dividing the maximum energy-saving potential into ten equal energy reduction intervals. The incentive-crediting scheme is formulated on a basis that proportionally more credits would be rewarded for diminishing investment return of consecutive reduction levels in a base building.

This paper examines the key issues involved in evaluating cost and benefits of various accredited criteria of an environmental assessment scheme in Hong Kong. Economic benefit–cost ratios have been developed for various criteria to help the developers and designers to identify the economic impact and cost effectiveness of the accredited criteria. Results of this analysis reveal that the economic benefit–cost ratios vary among different credits, and 24 out of total 56 credits could provide potential economic benefit for the developers and designers. Accordingly, a decision strategy for prioritising the criteria selection has been developed for the developers and designers. Besides, the use of economic benefit–cost ratios for revising the weighting scale within the performance-specific criteria is discussed.