Energy performance of windows in high-rise residential buildings in Hong Kong

At the present time in Hong Kong in its hot and humid climate, a single pane, clear glazing is most often used in windows of tall residential buildings. During this study, we employed HTB2, detailed building heat transfer simulation software, to evaluate a decrease in the yearly cooling load (Q) and in the peak cooling-load (D) in two residential flats due to different glazing single pane types and different flat orientations. The investigated glazing types were clear glazing, tinted glazing, reflective glazing, and tinted and reflective glazing.     

Design of a porous-type residential building model with low environmental load in hot and humid Asia

The purpose of this study is to propose a residential building model with voids which is appropriate for hot and humid regions of Asia with high population densities that also reduces the environmental load of buildings. This paper will explain an outline of a porous-type residential building model in Hanoi and the design process for introducing voids in buildings in order to improve natural cross ventilation effectively. Furthermore, the effects of natural ventilation, solar shading, and some devices for air conditioning systems for reduction the cooling and environmental load are estimated.     

Using passive cooling strategies to improve thermal performance and reduce energy consumption of residential buildings in U.A.E. buildings

Passive design responds to local climate and site conditions in order to maximise the comfort and health of building users while minimising energy use. The key to designing a passive building is to take best advantage of the local climate. Passive cooling refers to any technologies or design features adopted to reduce the temperature of buildings without the need for power consumption. Consequently, the aim of this study is to test the usefulness of applying selected passive cooling strategies to improve thermal performance and to reduce energy consumption of residential buildings in hot arid climate settings, namely Dubai, United Arab Emirates. One case building was selected and eight passive cooling strategies were applied. Energy simulation software – namely IES – was used to assess the performance of the building. Solar shading performance was also assessed using Sun Cast Analysis, as a part of the IES software. Energy reduction was achieved due to both the harnessing of natural ventilation and the minimising of heat gain in line with applying good shading devices alongside the use of double glazing. Additionally, green roofing proved its potential by acting as an effective roof insulation. The study revealed several significant findings including that the total annual energy consumption of a residential building in Dubai may be reduced by up to 23.6% when a building uses passive cooling strategies.     

Application of switchable glazing to high-rise residential buildings in Hong Kong

For typical high-rise residential building in Hong Kong, we evaluated the impact of using switchable glazing on energy use for space cooling. By using software EnergyPlus, it was found that application of switchable glazing would lead to a reduction in annual cooling electricity consumption by up to 6.6% where the actual amount depends on existence of overhangs, orientation of building wings, types and locations of rooms. Energy saving by this magnitude, however, cannot justify use of switchable glazing in residential buildings in Hong Kong, mainly because of the high glazing cost.     

A study of the effectiveness of passive climate control in naturally ventilated residential buildings in Singapore

Singapore has the hot and humid climate throughout the year. Many passive climate control methods are adopted in the naturally ventilated residential buildings to help achieve thermal comfort and reduce the energy consumption of air-conditioning. A field measurement and computational energy simulations were conducted to examine the effectiveness of commonly used passive climate control methods for these buildings. The effect of building orientation, façade construction, special roof system and window shading device on indoor thermal environment and cooling load was studied. The surface temperature of external wall and indoor thermal environment was measured to analyze the façade thermal performance. The cooling load was simulated to evaluate the effectiveness of various passive climate methods. Using the special roof system as thermal buffer is the most efficient method to reduce the room cooling load.     

The impacts of ventilation strategies and facade on indoor thermal environment for naturally ventilated residential buildings in Singapore

The impacts of various ventilation strategies and facade designs on indoor thermal environment for naturally ventilated residential buildings in Singapore are investigated in this study based on thermal comfort index. Four ventilation strategies, nighttime-only ventilation, daytime-only ventilation, full-day ventilation and no ventilation were evaluated for hot-humid climate according to the number of thermal discomfort hours in the whole typical year on the basis of a series of TAS simulations. Parametric studies of facade designs on orientations, window to wall ratios and shading devices were performed for two typical weeks by coupled simulations between building simulation ESP-r and CFD (FLUENT). The results indicate that full-day ventilation for indoor thermal comfort is better than the other three ventilation strategies. With various facade design studies, it was found that north- and south-facing facades can provide much comfortable indoor environment than east- and west-facing facades in Singapore. It is recommended that optimum window to wall ratio 0.24 can improve indoor thermal comfort for full-day ventilation and 600 mm horizontal shading devices are needed for each orientation in order to improve thermal comfort in further.     

Evaluating the potential impact of global warming on the UAE residential buildings – A contribution to reduce the CO2 emissions

There is significant evidence that the world is warming. The International Panel of Climate Change stated that there would be a steady increase in the ambient temperature during the end of the 21st century. This increase will impact the built environment, particularly the requirements of energy used for air-conditioning buildings. This paper discusses issues related to the potential impact of global warming on air-conditioning energy use in the hot climate of the United Arab Emirates. Al-Ain city was chosen for this study. Simulation studies and energy analysis were employed to investigate the energy consumption of buildings and the most effective measures to cope with this impact under different climate scenarios. The paper focuses on residential buildings and concludes that global warming is likely to increase the energy used for cooling buildings by 23.5% if Al-Ain city warms by 5.9 °C. The net CO₂ emissions could increase at around 5.4% over the next few decades. The simulation results show that the energy design measures such as thermal insulation and thermal mass are important to cope with global warming, while window area and glazing system are beneficial and sensitive to climate change, whereas the shading devices are moderate as a building CO₂ emissions saver and insensitive to global warming.     

夏热冬冷地区遮阳及自然采光节能优化设计

对于夏热冬冷地区,建筑外遮阳是一种非常有效的节能措施,不仅可以有效降低冷负荷,而且能够阻挡眩光,提供舒适的视觉环境,但是对自然采光有一定影响。借助能耗模拟软件Energyplus建立了上海某高层办公楼建筑模型,在采用自然采光和人工照明自动控制的条件下,模拟不同朝向采用不同形式的遮阳对建筑整体能耗及室内光环境产生的影响,通过比较后得出各个朝向的最佳遮阳形式。     

Investigation on energy performance and energy payback period of application of balcony for residential apartment in Hong Kong

The provision of balcony to the living room of a residential flat offers a number of merits including improved view enjoyment, enhanced ventilation and increased planting space. In addition, a balcony can act as an overhang and provide solar shading as well as electricity saving of the air-conditioning system. This paper reports the findings on the energy and environmental impact due to the provision of a balcony. In this study, a typical residential flat with balcony constructed at the living room was modeled and the energy performance was investigated with the use of the typical weather data set of a subtropical city, Hong Kong. The effects of balcony's orientation and glazing material of window were also evaluated. It was found that the residential flats facing various orientations (N, E, S, W, NE, SE, SW and NW) can offer substantial energy saving in air-conditioning system due to the shading effect of balcony. The building case with southwest facing balcony and clear glass glazed window gave the highest saving percentage of 12.3% in annual air-conditioning consumption. In terms of cost payback period, the values were estimated as 25.9 years (based on extra construction cost of a balcony) and over 100 years (based on extra purchasing cost), respectively. On the other hand, the energy payback period was 22.4 years for this building case. The provision of balcony to the living room of residential flat was found environmentally feasible in Hong Kong.     

基于光热性能的南向遮阳措施节能降耗模拟研究

采用模拟耦合计算室内照度与窗体能耗的方法,以上海为研究区域,针对朝南方向,分析了水平、垂直遮阳板以及卷帘等不同装置引起的照明能耗和制冷能耗之和,并由此评价其节能降耗的效果.结果表明,当灯具光效大于41.2 Lm/W时,遮阳卷帘引起的综合能耗较小;而当光效小于上述数值时,水平遮阳板更好.这两种遮阳措施下室内的照度分布相对...     

Thermal performance modelling of complex fenestration systems

Complex fenestration systems (CFS) have become standard elements in facade design of high performance buildings. They include, for example, shading devices to control illumination, solar heat gains, glare and view-out, and photovoltaic elements imbedded in glazing layers to produce electrical energy on site. However, current methodologies to evaluate the thermal performance of CFS are limited to few products and types. This article develops a general methodology to compute the thermal performance of CFS. The methodology assumes each system layer as porous with calculated effective radiation and thermal properties. A new thermal penetration length model was developed to account for the effects of porous layers on the convective film coefficients of adjacent gas spaces, and applied to various types of shading devices. This methodology is validated using the available measurement and computational fluid dynamics (CFD) simulation results for the U-factor of double-glazed windows with between-pane and internal blinds.     

基于遗传算法的绿色建筑优化设计

建筑师在实际运用建筑节能设计标准过程中感觉标准较复杂、不方便。将遗传算法在多目标优化设计中的优势与建筑能耗仿真软件结合起来,建立一套绿色建筑优化设计方法或模型。以武汉地区住宅建筑为例,在最低能耗与最低成本的目标控制下,同时,优化设计建筑朝向、窗墙比、外墙构造、屋面构造、采暖温度设定点、空调温度设定点、遮阳系数、窗户玻璃类型的组合因素。将优化结果与现有绿色节能建筑设计规范进行对比,给出了绿色建筑设计中部分参数的新的参考值。     

“SOLVENT”: development of a reversible solar-screen glazing system

Preliminary experiments with a novel glazing system developed at the Desert Architecture and Urban Planning Unit of Ben-Gurion University of the Negev in Israel indicated that it may provide improved visual and thermal performance in buildings with large glazed areas located in sunny regions, regardless of orientation. In winter, it reduces glare, local over-heating and damage to furnishings caused by exposure to direct solar radiation, with only a small reduction in solar space heating. In summer, it reduces the penetration of unwanted radiation without obstructing the view through the window, to an extent that may render external shading devices unnecessary. The SOLVENT project was contracted to complete the development of the glazing system, which is based on the concept of converting short-wave solar radiation to convective heat and long wave radiation. The glazing system was modeled and evaluated experimentally; a suitable frame was developed for it; and a design tool required for its application was developed. The current paper reports on physical modeling and experimental evaluation of the glazing system.     

Energy simulations for glazed office buildings in Sweden

Highly glazed buildings are designed by architects to be airy, light and transparent with more access to daylight. Their energy efficiency, however, has become questioned. Therefore, energy simulations of single skin office buildings in Sweden were carried out, using a dynamic energy simulation tool. In order to study the impact of glass on the energy use during the occupation stage, office building alternatives with 30, 60 and 100% window to external wall area were studied. Other varied parameters were the building's orientation, the plan type (open and cell plan offices), the control set points and the façade elements (type and size of windows, type and position of shading devices, etc.). The main conclusion is that careful design is needed to ensure low energy use and good thermal comfort, especially for highly glazed office buildings. Careful design of glazed office buildings has to be based on detailed thermal simulations. Especially in fully glazed buildings (in which the façade is more “sensitive” to climatic conditions), proper combination of control set points, glazing and solar shading are crucial for the energy performance.     

外呼吸双层通风玻璃幕墙热工性能模拟分析

对某建筑外呼吸双层通风玻璃幕墙内的速度场和温度场进行了模拟分析。讨论了遮阳设施、空气层宽度等因素对综合传热系数的影响。分析比较了外呼吸双层玻璃幕墙建筑和四种单层玻璃幕墙建筑的供暖空调能耗。结果表明,外呼吸双层通风玻璃幕墙是一种节能的生态建筑围护结构形式。     

Effect of various factors on the shading coefficient of different types of glazing

This is a study of the effects of various factors on the shading coefficient of different types of glazing. The main objective is to investigate the sensitivity of the shading coefficient to these factors and hence the validity of adopting a fixed value for the coefficient, as given in pertinent references, under different conditions. The study covers single and double glazing, of clear or heat-absorbing glasses, with and without reflective surface coatings. Plastic glazing is also included in the work.The variations of the shading coefficient with the incidence angle, the outdoor wind velocity, and the indoor air velocity are presented for the different types of glazing. The effect of windowpane(s) treatment, by applying reflective coats, is also exposed.The study revealed that, under certain conditions and with certain types of glazing, the use of the constant shading-coefficient values available in the literature may entail untolerable error in estimating the solar heat gain through glazed fenestration. In such cases the shading coefficient may have to be treated as a variable rather than a constant. However, this incurs excessive computational effort; therefore, it can be justified only when a high degree of accuracy is required which is not the case for routine air conditioning load estimations.     

Solar transmittance analysis of different types of sunshades in the Florida climate

Solar shading devices are an integral part of any building enclosure that impacts the building efficiency and indoor environment especially in the hot and humid climates like Florida. In order to design an energy efficient structure, the solar transmittance of the window-shade system needs to be determined in order to calculate how much total solar radiation they transmit. This paper presents the findings of a comparative study for evaluating the effects of different solar shading devices on the solar transmittance properties of windows with different orientations in the city of Miami, Florida. A rectangular office block was modeled and rotated clockwise in 60° interval from North to South to study the variations in the transmission properties of windows. Commercially available shading products were analyzed under three broad categories, i.e. external, interpane and internal and each type was simulated with six different orientations: North (N), Northeast (NE), Southeast (SE), South (S), Southwest (SW), Northwest (NW). The climatic data file was produced by the software METEONORM. The simulation results were compared to determine a performance metric for the primary and the total solar transmittance of each window-shade system. After selecting the most efficient solar devices, a thermal analysis was performed to estimate the reduction in cooling loads generated by improving the internal operative environment.     

Impact of passive climate adaptation measures and building orientation on the energy demand of a detached lightweight semi-portable building

The building energy demand for heating and cooling is changing due to climate change. The adoption of climate change adaptation measures at the building scale aims at limiting heating and cooling demands. In previous studies on adaptation measures little attention has been paid to lightweight semi-portable buildings, which are increasingly used to temporarily house the growing number of small households (1–2 persons) in peripheral and derelict areas. In this paper the impact of passive climate adaptation measures and building orientation on heating and cooling demands is assessed for a detached, lightweight, semi-portable residential building by means of building energy simulations (BES), considering two climate scenarios for the Netherlands: current climate and a future climate (2050). The results show that the most efficient adaptation measure consists in a combination of exterior solar shading and an increase of thermal resistance of the building envelope, which reduces the annual heating and cooling demand–averaged over eight building orientations – by 11% for the current climate and 15% for the future climate. The impact of building orientation varies according to the climate scenario. Compared to the average over the eight orientations considered, the annual cooling demand for a single orientation varies between about ?31% and +22% and between about ?24% and +18% for the current and future climate, respectively. For the case without adaptation measures, optimizing the building orientation leads to annual total energy savings of about 4% for the current and 3% for the future climate.     

A study of solar heat gain to multistorey buildings in hot and arid regions

The paper presents an empirical study of solar heat gain to multistorey buildings at the peak degree hour on the hottest day of summer in hot and arid regions of India. The effects of surface to floor area ratio of a building form, orientation, fenestration percentage and shading devices on the cooling loads have been quantified. Case studies simulating realistic situations have been subjected to empirical calculations by computer.Conclusions drawn from the results afford a guideline to practising architects and air-conditioning engineers to make suitable adjustments at the initial building design stage in order to reduce the cooling loads caused by solar radiation.Finally, a field study demonstrates the possibility of reducing solar heat gain by striking a compromise between scientifically recommended shading devices and architecturally acceptable forms of external louvres.     

建筑外遮阳节能技术研究

建筑遮阳对建筑隔热、保温、抵御紫外线等具有重要作用,建筑外遮阳的有效设置可以将80%太阳辐射或直射反射出去,降低室内太阳得热,保护建筑物,降低空调负荷。设置遮阳的建筑能够改善窗户隔热性能,使建筑制冷用能节约25%以上,提高窗户保温性能,节约建筑采暖用能10%以上,节能效果良好。