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• Automatic MiC envelopes and layout generation by a novel SSG-MOO method. • Multi-objective optimization formulation for passive MiC design. • A pilot MiC study in Hong Kong produced 5 selected Pareto optima out of 625. • Up to 0.42% energy savings and 9.71% spatial daylight autonomy improvement against the baseline. • A multi-level analysis of results and design strategies for practitioners. Modular-integrated Construction (MiC) is an emerging construction technique promoted in the building sector for high productivity and low waste emission in the construction phase; yet, the standardized modules also bring new challenges, such as balancing passive energy efficiency and spatial daylight autonomy, to the operational phase. This paper proposes a Symmetric Skeleton Grammar-based Multi-Objective Optimization (SSG-MOO) method to formulate parametric MiC envelopes and detailed layout, with the two objective functions being energy efficiency and interior daylight performance in the operational phase. Pareto optima of the SSG-MOO, computed by the Non-dominated Sorting Genetic Algorithm II, are generally verified and analyzed in three levels, i.e., MOO's solution space, SSG layout, and MiC design parameters. A case study of MiC residential building in Hong Kong demonstrated the SSG-MOO method through five new passive MiC designs (i.e., spatial reorganization of three architectural modules, and parameter tuning of the envelops and corridors), achieving up to 0.42% energy savings and 9.71% spatial daylight autonomy improvement compared to the baseline design. The contribution of this paper is two-fold, including a novel and sound SSG-MOO formulation for parametric MiC designs, and offering time-efficient and evidence-based design tactics for MiC designers and industrial practitioners to push boundaries of MiC. [ABSTRACT FROM AUTHOR]

Buildings are responsible for about 92% of the total energy end-use in Hong Kong, of which above 70% is from the commercial sector. Most of the buildings in Hong Kong are high-rise, and approximately 15% of the total building stock is commercial buildings. Despite the considerable improvement in the understanding of the life cycle energy use of office buildings, there is still a lack of research into the life cycle energy demand of high-rise office buildings. Such knowledge is however essential for facilitating building energy conservation in the high-rise urban environment. The aim of this paper is to investigate the life cycle energy use of high-rise office buildings. The research was carried out through a critical literature review and case studies of ten real-life high-rise office buildings in Hong Kong. Results show that the life cycle energy consumption is 51.78–73.64 GJ/m 2 over the 50-year study period. Building operation consumes 78–89% and the rest (i.e. 11–22%) is taken by the embodied energy. Despite the distinction in terms of the amount of embodied energy between high-rise buildings and low-rise counterparts, no clear correlation is found between building height and embodied energy intensity. Moreover, energy use for material manufacturing and transport should be prioritised in reducing the embodied energy, of which the transport energy needs to be taken into extra consideration for the case of Hong Kong. The findings should inform construction industry participants of the significant potential in reducing the embodied energy of high-rise office buildings. The paper profiles the life cycle energy use of high-rise office buildings and should be important for the policy formulation towards the holistic energy conservation in high-rise buildings over their lifespans. [ABSTRACT FROM AUTHOR]

Buildings are a main contributor to energy consumption and carbon emissions. The approach of low energy or low carbon building has been widely adopted. However, there exist challenges for energy and carbon modeling, particularly of high-rise buildings in high-density urban environments. The aim of this paper is to examine the challenges and develop strategies for energy modeling of high-rise buildings drawing on the case of public housing in Hong Kong. The paper reviews the knowledge barriers to the use of building energy analysis software and proposes a workflow to incorporate energy simulation into the design stage. Considering the urban environmental factors that may contribute to biased results of energy simulation, the technical issues during the conversion of data from BIM model to energy simulation software are investigated. Thermal zones and user behaviors are also examined as technical and subjective assumptions could lead the simulation to a wrong direction. The examined challenges and developed strategies will help achieve building energy simulation and carbon emission estimation of high-rise buildings in Hong Kong with efficiency and accuracy and also inform practices in other relevant urban settings. [ABSTRACT FROM AUTHOR]

Abstract: Building cooling load prediction is one of the key factors in the success of energy-saving measures. Many computational models available in the industry have been developed from either forward or inverse modeling approaches. However, these models usually require extensive computer resources and lengthy computation. This paper discusses the use of the multi-layer perceptron (MLP) model, one of the artificial neural network (ANN) models widely adopted in engineering applications, to estimate the cooling load of a building. The training samples used include weather data obtained from the Hong Kong Observatory and building-related data acquired from an existing prestigious commercial building in Hong Kong that houses a mega complex and operates 24h a day. The paper also discusses the practical difficulties encountered in acquiring building-related data. In contrast to other studies that use ANN models to predict building cooling load, this paper includes the building occupancy rate as one of the input parameters used to determine building cooling load. The results demonstrate that the building occupancy rate plays a critical role in building cooling load prediction and significantly improves predictive accuracy. [Copyright &y& Elsevier]

Improving the energy performance of existing building refurbishment has been identified as one of the key measures to reduce greenhouse gases (GHGs) emissions and combat climate change. However, little has been done to uncover how human behaviours would affect the selection of refurbishment solutions selection. The problem is particularly obvious for high-rise residential buildings as they are owned and/or occupied by different peoples with idiosyncratic behaviour and preference. In this research, 46 potential methods commonly used for major sustainable building refurbishment in high-rise residential buildings located in cities with sub-tropical climate like Hong Kong were identified through literature review. These sustainable building refurbishment methods are classified under five groups namely energy user pattern, domestic, high-rise building, climate feature and other building characteristics. A questionnaire survey was conducted to examine the feasibility of the identified refurbishment methods based on the perception of owners and occupants. The results show that those methods classified under building services category such as lighting, appliance, ventilation and lift received greater support from owners and occupants. It is interesting to note that owners and occupants did not favour those sustainable refurbishment options which are related to the building envelop when it comes to major building refurbishment. As for the renewable energy refurbishment methods, their acceptability was moderate indicating that there is huge potential for being incorporated into the major building refurbishment. This paper should help improve our understanding on what factors contribute to the satisfaction of owners and occupants of high-rise residential building in a major sustainable refurbishment scheme. [ABSTRACT FROM AUTHOR]

Abstract: In subtropical Hong Kong, buildings consume the most of the electricity use. Computer simulation technique is a useful tool for predicting building thermal and energy performance. Simulation computer programs require weather data input to drive the mathematical models within the simulation tools for comparative studies and annual energy estimation. Typical weather year data representing the long-term climatic conditions are often used. Recently, there has been an increasing interest in incorporating daylight in the architectural and building designs to reduce building energy consumption. However, daylight parameters are not always available. In 2003, the International Commission on Illumination (CIE) adopted a range of 15 standard skies covering probably the whole spectrum of the usual skies in the world. Once the skies have been identified, the basic solar irradiance and daylight illuminance at various inclined planes can be obtained. This paper presents the work on the development and evaluation of two typical weather datasets, namely Typical Meteorological Year (TMY) and Test Reference Year (TRY). Measured hourly weather data for the 30-year period from 1979 to 2008 were analysed. Building energy simulations were conducted to evaluate the two weather datasets. Daylight parameters were derived using luminous efficacy approach and the sky conditions were categorized based on common climatic variables. [Copyright &y& Elsevier]

Abstract: The shading-type building-integrated photovoltaic (BIPV) claddings can act as power generators as well as external shading devices of a building, which reduce the energy consumption of the building. However, there is little information about energy impacts of different tilt angles of the shading-type BIPV claddings. By considering the typical meteorological conditions of Hong Kong, the energy performance of the shading-type BIPV claddings, in terms of the electricity generation and the cooling load reduction, is analyzed in this paper. The optimum tilt angle of PV modules for maximum electricity generation is found to be 20° instead of local latitude. Combining electricity generation and cooling load reduction, it can be concluded that the optimum tilt angles for the first type of the shading-type BIPV claddings vary from 30° to 50°, while the optimum tilt angle for the second type is 0°. [Copyright &y& Elsevier]

Abstract: High ventilation rate is shown to be effective for reducing cross-infection risk of airborne diseases in hospitals and isolation rooms. Natural ventilation can deliver much higher ventilation rate than mechanical ventilation in an energy-efficient manner. This paper reports a field measurement of naturally ventilated hospital wards in Hong Kong and presents a possibility of using natural ventilation for infection control in hospital wards. Our measurements showed that natural ventilation could achieve high ventilation rates especially when both the windows and the doors were open in a ward. The highest ventilation rate recorded in our study was 69.0 ACH. The airflow pattern and the airflow direction were found to be unstable in some measurements with large openings. Mechanical fans were installed in a ward window to create a negative pressure difference. Measurements showed that the negative pressure difference was negligible with large openings but the overall airflow was controlled in the expected direction. When all the openings were closed and the exhaust fans were turned on, a reasonable negative pressure was created although the air temperature was uncontrolled. The high ventilation rate provided by natural ventilation can reduce cross-infection of airborne diseases, and thus it is recommended for consideration of use in appropriate hospital wards for infection control. Our results also demonstrated a possibility of converting an existing ward using natural ventilation to a temporary isolation room through installing mechanical exhaust fans. [Copyright &y& Elsevier]

Abstract: Double skin façade can be defined as a building façade covering one or several stories with multiple skins. The skins may be air tight or ventilated. With sophisticated study and design, buildings constructed with double skin façade can have better thermal performance than the conventional single skin façade. This paper reports the findings on the energy performance of double skin façade applied to a typical office building under the climatic condition in Hong Kong. An experimental setup was established and the measured data were used to verify the theoretical model developed via the EnergyPlus simulation program. The validated model was then used to evaluate the energy performance of double skin façade with various configurations including glazing type (clear, absorptive or reflective glass), glazing position (inner or outer pane) and glazing layers (single or double glazing material). The results indicate that a double skin façade system with single clear glazing as the inner pane and double reflective glazing as the outer pane can provide an annual saving of around 26% in building cooling energy, as compared to a conventional single skin façade with single absorptive glazing. However, the long payback period of 81 years makes the double skin façade system economically infeasible. Support and motivation are needed from the local government in order to foster successful and widespread application of the double skin façade system in buildings. [Copyright &y& Elsevier]

Abstract: Hong Kong is located in a typical subtropical region. The buildings in Hong Kong are subjected to high cooling demands for their air-conditioning systems throughout most of the year, and their contribution toward the total energy consumption is about 40%. Therefore, energy efficiency in buildings is essential to reduce the global energy use and improve the local environmental sustainability. This paper provides an overall review of the building energy research and efforts in Hong Kong over the last decade. Various aspects and energy saving measures, including energy policy, energy audit, design, control, diagnosis, building performance evaluation and renewable energy systems, studied or used to enhance the energy efficiency in buildings are reviewed. A brief introduction of the Hong Kong Building Energy Codes (BEC) and Hong Kong Building Environmental Assessment Method (HK-BEAM) are also provided to present the efforts of the local government and community on energy efficiency in buildings. This review aims at providing building researchers and practitioners a better understanding of buildings energy saving opportunities and approaches in cities particularly in subtropical regions and taking further proper actions to promote buildings energy efficiency and conservation. [Copyright &y& Elsevier]

Abstract: Accurate prediction of building energy performance requires precise information of the local climate. Typical weather year files like test reference year (TRY) and typical meteorological year (TMY) are commonly used in building simulation. They are also essential for numerical analysis of the sustainable and renewable energy systems. The weather year file of one city is often employed by the nearby cities for such purposes. In this paper, the developments of customized weather year formulation are reviewed. The key issues are discussed making reference to two neighboring cities, Hong Kong and Macau, using their weather data records over a century, and the typical weather year files developed. The findings support the preference of TMY over TRY. It is also suggested that the TMY selection process should include the most recent meteorological observations, and should be periodically reviewed to well reflect the long-term climate change. [Copyright &y& Elsevier]

Due to the hot and humid weather, the majority of residential units in Hong Kong are equipped with window-type air-conditioners. However, the provisions made in the building envelope design for their installation are often inadequate, particularly in the clearances for intake and disposal of outdoor air for condenser cooling. Consequently, the air-conditioners would consume an unnecessarily high amount of electricity and at the same time output less cooling. The paper describes a study on the outdoor airflow around air-conditioners in residential buildings and the related thermal phenomena. The CFD code FLUENT was employed to predict the airflow patterns in 20 installation configurations of window-type air-conditioners, which embrace different shapes of clearances around the air-conditioners that are on the same story in a building. The results reveal that insufficient clearance spaces could cause a significant increase in the temperature of the outdoor air entering the air-conditioners, which would also be accompanied by a reduction in the airflow rate. The increase in the electricity consumption of the air-conditioners could exceed 45% for the case where the air-conditioners were drawing in the discharged hot condenser air from other air conditioners located at an opposite wall for condenser cooling. The presence of a sidewall, however, could cause the discharged hot air to move quicker away from the air-conditioner leading to a lower entering air temperature to its condenser. [Copyright &y& Elsevier]

Reducing building energy demand plays a vital role in addressing the depletion of energy resources and energy-related environmental issues. Previous research identified the statistical correlations between embodied energy and costs of buildings. However, little research has explored the relationship between operational energy and life cycle cost performance of buildings. This paper aims to investigate the energy efficiency and cost effectiveness of energy saving measures (ESMs) and thereby identify the relationship between operational energy and life cycle cost performance of high-rise office buildings. Five types of ESMs with 32 scenarios were examined using a real-life 35-storey office building in Hong Kong as a typical high-rise high-density city. The five types of ESMs are (1) increase temperature setpoint, (2) adopt daylighting sensors and light-emitting diode lamps (3) replace with low-e glass, (4) upgrade heating, ventilation and air conditioning system, and (5) implement on-site renewable energy. The results discover a U-curve relationship between operational energy saving and initial investment cost of the five ESMs. Moreover, the results show a significant linear correlation between operational energy saving and net present value of the ESMs. Such relationship reveals trade-off and synergy effects largely existing between opertional energy and cost performance in improving energy efficiency of high-rise offic buildings. This research suggests that increasing indoor temperature setpoint should be prioritised in lowering operational energy. The results are also discussed drawing on the findings of previous studies in other city contexts. This research contributes a novel life cycle perspective to future systematic research into building energy and economics. The findings are important to building designers in their decision-making of reducing buildings' operational energy consumption in a cost-effective way. • Cost effectiveness of different energy saving measures (ESMs) varies significantly. • U-curve relation is found between energy saving and initial investment of buildings. • Linear correlation is found between energy saving and net present value of building. • Variations in cost effectiveness of ESMs lead to the found energy-cost relations. • Cost effectiveness of renewable technology relies much on financial incentives. [ABSTRACT FROM AUTHOR]

The rapid growth of energy consumption in buildings has become an alarming threat to the climate. Various building-level energy saving measures have been studied and adopted to achieve energy efficiency. However, high-rise public residential buildings in subtropical climate as an important contributor to building-level energy consumption have received insufficient attention of research. The aim of this paper is to analyse the energy use of high-rise residential buildings in subtropical climate and examine the impacts of different energy saving measures for developing strategies for achieving very low-energy high-rise buildings. A typical high-rise (40-storey) public residential building in Hong Kong was selected as the case building, which has the energy use intensity of 106.6 kWh/m2 for the total building area and of 153.8 kWh/m2 for the area inside the residential units. The energy model of the case building developed using EnergyPlus software was carefully calibrated using metered energy use data and expert consultations adopting a systematic approach. Sensitivity analyses were then conducted using the parametric analysis tool jEPlus to quantify the impacts of different energy saving measures on energy use intensity reduction. It was found the measures in relation to human behaviours have the largest impact, followed by building service system efficiency and renewable energy. Building form and building envelope have the modest impact. The findings enhance the knowledge of subtropical high-rise public residential buildings' energy performance, and the developed and calibrated energy model could be used to explore more strategic energy saving measures in the long term. The quantified impacts of the measures should inform design decisions of low-energy housing production in high-rise sectors. • A 40-storey building is examined with energy use 153.8 kWh/m2 for residential area. • Energy model uses EnergyPlus software with sensitivity analyses tool jEPlus. • Behaviours have largest impact on energy use, then building services and renewables. • Building form and envelope have the modest impact on energy use reduction. • Systemic strategies are suggested for very low-energy high-rise residential buildings. [ABSTRACT FROM AUTHOR]

• There are wide opportunities for zero-carbon building policy formulation for Hong Kong. • Risks co-exist, particularly geographic ones, but are outweighed by opportunities. • Opportunities and risks are complex, interactive, interchangeable and context-specific. • Recommendations for mitigating the risks highlight policy and business strategy. • Stakeholder partnership and government and client leadership are critical. There is a worldwide policy agenda of reducing buildings' carbon emissions. Zero-carbon building has emerged as an advanced model with policy support, but high-rise remains a knowledge gap. This paper aims to contribute a better understanding of the opportunities and risks of formulating and implementing a zero-carbon building policy, and identify recommendations for maximising the opportunities and minimising the risks. Hong Kong as a typical high-rise high-density city was considered as the case for study. The research was conducted through the combination of a policy review, a questionnaire survey, interviews and focus group meetings with several hundred professionals and stakeholders carefully selected using stratified sampling. Wide opportunities were identified, with most important ones including raising public awareness of sustainable living, reducing buildings' energy use and carbon emissions, and promoting strategic urban planning. However, risks were found to co-exist, with most significant ones including geographical obstacles to domestic renewable energy generation, heavy reliance on fossil fuels, and resistance of practitioners to the policy. Nevertheless, the opportunities were considered to outweigh the risks. Recommendations were identified to mitigate the risks, which are centred on policy guidance, business strategy, stakeholder partnership, and government and client leadership. The findings reveal the complex, interactive, interchangeable and context-specific features of the opportunities and risks, which alert to reconstruct a dialectical system framework of implementing zero-carbon building policy for Hong Kong. The yielding policy implications and recommendations should shape the reconstruction of that framework for high-rise high-density cities. [ABSTRACT FROM AUTHOR]

Air-conditioned offices in the subtropics are recommended to operate within specified ranges of indoor temperature, relative humidity, air velocity, and carbon dioxide concentration for thermal energy conservation. As environmental discomfort leads to productivity loss, this study investigates the impact of an indoor environmental policy on Grade A offices served by different airside systems in terms of energy consumption, thermal comfort, and productivity loss. Occupant thermal response is specifically considered as an adaptive factor in the evaluation of energy consumption and productivity loss. Simple Monte Carlo sampling technique was applied to determine the input parameters referenced from literatures for simulation. The findings indicate that the reduction of clothing value improves thermal sensation and should be addressed in the environmental policy to ensure a thermally comfortable indoor environment.Practical application: This study is a useful reference source for evaluating indoor thermal environmental policies for air-conditioned offices in subtropical climates. Implication of clothing value in thermal sensation should be addressed in the environmental policy to ensure a thermally comfortable indoor environment of air-conditioned offices. [ABSTRACT FROM AUTHOR]