Heat transfer modelling on windows and glazing under the exposure of solar radiation

Due to the effect of solar radiation on windows and glazing system the evaluation of heat flow is of primary importance in modeling the thermal performance within building interiors to account thermal comfort and overall energy consumption of a building. In this context the optical properties of window glazing are measured to determine the percentage absorption of incident solar radiation. An experimental study was performed in a room to measure the glazing surface temperature due to the global radiation on it. The corresponding window plane global radiation and horizontal global radiation were measured outside for simulation. Mathematical models have been developed to simulate the window plane solar radiation and corresponding glazing surface temperature aiming at validating the measured values. The thermal model is concerned with laminar heat transfer for natural and forced convection process according to the ambient conditions. The estimated errors between experimental and simulated values of window plane radiation and glazing temperature are shown to be within ±5%. Using the developed thermal model the heat flow inside the room through windows is determined. Thus overall heat transfer coefficient of glazing (U-factor) and the Solar Heat Gain (SHG) of building interior have been predicted from the simulation.     

Thermal performance of courtyard buildings

In this analysis, the energy performance of a courtyard in buildings is investigated under conditions of different factors of climate, height, glazing type, and glazing percentage. The courtyard design used for the analysis was square in plan and surrounded by the building on all four sides. The glazing type and percentage for the courtyard walls were varied in the analysis. Weather data from four cities representative of climatic conditions of cold, temperate, hot-humid, and hot-dry were used. The computer energy simulation program DOE2.1E was used in this analysis as a tool to evaluate the impact of these factors on the energy consumption of the buildings. The results of the parametric simulation showed that the courtyard building thermal performance differed from climate to climate and even the impact of the measures or the variables on cooling, heating, and the total annual energy consumption differed with different variables’ configuration. In general, the open courtyard building exhibits a better energy performance in hot-dry and hot-humid climates.     

Analysis of annual heating and cooling energy requirements for office buildings in different climates in Turkey

A great amount of world energy demand is connected to the built environment. Electricity use in the commercial buildings, accounts for about one-third of the total energy consumption in Turkey and fully air-conditioned office buildings are important commercial electricity end-users since the mid-1990s. In the presented paper, the interactions between different conditions, control strategies and heating/cooling loads in office buildings in the four major climatic zones in Turkey – hot summer and cold winter, mild, hot summer and warm winter, hot and humid summer and warm winter – through building energy simulation program has been evaluated. The simulation results are compared with the values obtained from site measurements done in an office building located in Istanbul. The site-recorded data and simulation results are compared and analyzed. This verified model was used as a means to examine some energy conservation opportunities on annual cooling, heating and total building load at four major cities which were selected as a representative of the four climatic regions in Turkey. The effect of the parameters like the climatic conditions (location), insulation and thermal mass, aspect ratio, color of external surfaces, shading, window systems including window area and glazing system, ventilation rates and different outdoor air control strategies on annual building energy requirements is examined and the results are presented for each city.     

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.     

Potential of emerging glazing technologies for highly glazed buildings in hot arid climates

In order to improve the sustainability of buildings one of the challenges is to address the role of the building envelope as the key climate moderator between the internal and external environments. The envelope is exposed to the elements and needs to control air exchange as well as sunlight and sound passing through to the occupants. Therefore, it has a major impact not only on the energy utilisation within the space it controls but also on the quality of comfort. However, inside highly glazed modern buildings, achieving good comfort is often at the cost of high-energy consumption. Therefore, in the light of ever increasing energy costs, improved façade design can contribute to a reduction of operational costs. The aim of this paper is to explore technical, economic, environmental and indoor comfort implications of emerging glazing technologies for energy control of highly glazed buildings in arid Middle Eastern climates, which is one of the harshest climates for this building type. The work includes predictions through thermal simulation of the impact of electrochromic glazing, holographic optical elements (HOE), aerogel glazing and thin film photovoltaics on two example buildings. Potential reductions in cooling demand are assessed.     

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.     

Energy saving in the conventional design of a Spanish house using thermal simulation

During the last decade, regulations designed to change the way of designing, building, maintaining, renovating and demolishing buildings and their surroundings have been developed at European level. However, sustainability targets shift throughout the life of a building and design solutions should go beyond strict compliance with each country's regulations. This study prioritises a building's energy behaviour during its use. It demonstrates the value of combining simple passive strategies with thermal simulation tools in standard architectural design practice. To achieve this, we started from the conventional design of a house in the North of Spain, applying passive techniques to achieve energy savings and environmental improvements that exceed regulatory requirements. Simple heating and cooling practices are incorporated into the design. The final house combines all favourable actions that manage to reduce consumption, especially during the most intense winter period. The final design is fully south facing, with an additional 20% glazing in the north and south façades, a 35-cm lintel in the window frames and an additional 2 cm insulation on the façade. Simulation reduced overall thermal consumption by almost 13%. The embodied energy used for the improvements is barely significant. Although the additional investment is arguably not profitable in economic terms, the increased investment is minimal in comparison with total investment in the building.     

Energy modelling studies of thermochromic glazing

Theoretically thermochromic glazing has the potential to reduce energy consumption in buildings by allowing visible light for day lighting, reducing unwanted solar gain during the cooling season, whilst allowing useful solar gain in the heating season. In this study building simulation is used to predict the savings made by novel thermochromic glazing coatings compared to standard products, for locations with different climates. The results suggest that thermochromic glazing can have a significant energy saving effect compared to current approaches.     

武汉地区双层玻璃幕墙应用的适应性研究

武汉地区建筑围护结构的保温隔热性能差,致使冬夏季节空调制冷制热能耗高。采用双层玻璃幕墙可降低武汉地区的建筑能耗,提高建筑室内热环境的舒适度,将给武汉地区带来巨大的经济效益和社会效益。     

玻璃窗在建筑节能中的作用及其特性分析

本研究根据中国不同地区的气候特点,利用玻璃窗模拟软件Window5.1和建筑环境设计模拟分析软件DeST2,以一个典型住宅建筑模型为研究对象,通过模拟计算9种典型玻璃窗的热工特性以及冬季供暖和夏季供冷的能耗,分析并评估了不同类型玻璃窗的节能特性和对建筑能耗的影响。从而可得出如下结论:在严寒和寒冷地区建议采用中空高透射Low-e玻璃窗;在夏热冬冷地区选用中空 内遮阳窗户类型可比普通单窗节能近20%;而在夏热冬暖地区可以选择低透射Low-e玻璃窗、中空 内遮阳模式或者普通单玻 内遮阳模式均可达到理想的节能效果。为将来的建筑外窗节能设计以及玻璃窗的合理选型设计提供参考依据。     

不同类型玻璃在北京地区的节能研究

分别采用5种不同传热系数和遮阳系数的外窗玻璃,利用建筑能耗模拟软件eQUEST模拟北京地区某办公建筑的能耗,研究分析在北京地区玻璃的传热系数和遮阳系数对办公建筑逐月冷热负荷的影响;在全年能耗方面,6mm白玻+12mm空气+6mm白玻、6mm Low-E玻璃+12mm空气+6mm白玻、4mm超白玻+13.5mm气凝胶+4mm白玻、气凝胶玻璃(遮阳型)相对于12mm白玻的节能率分别为2％、11％、1％、13％,通过分析比较得出气凝胶玻璃这一新型建筑材料具有较好的节能效果.     

The predicted impact of roof aperture design on the energy performance of office buildings

An investigation has been made of potential lighting electricity reductions and associated thermal impacts of replacing electric light with sunlight admitted through rooftop glazing on a single-story, prototypical office building. Experimental scale models have been used to determine the fraction of the solar radiation entering the aperture which reaches the work plane as useful illumination. This information is used in a developmental version of the building energy analysis computer program BLAST-3.0 to predict reductions in lighting electricity and the impacts on energy consumption for heating and cooling the building. The results indicate that a large fraction of the electricity consumed for lighting a single-story office building can be displaced using modest amounts of glazing in the roof. Also, both heating and cooling energy consumption reductions are possible from a daylighting system, but they are substantially smaller than the potential lighting electricity reductions. The design implications of the results are discussed and future directions for the work are outlined.     

Investigation on energy performance of double skin façade in Hong Kong

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.     

夏热冬冷地区三维空间视角下住宅南向窗节能研究

外窗属于外围护结构之一,是建筑的重要组成部分,也是建筑保温中最薄弱的环节。窗的开设与建筑节能密切相关。夏热冬冷地区南向窗应属整套住宅建筑的主要采光源,其窗户面积大小变化对采光率影响较大。以夏热冬冷地区——桂林市南向窗采光良好条件为基础,以"窗墙面积比"和"窗地面积比"作为研究变量,以能耗模拟软件Ecotect模拟作为研究方法,在三维空间视角下进行建筑热环境模拟研究,确定了南向房间节能的"窗墙面积比"与"窗地面积比"取值范围,为今后的夏热冬冷地区——桂林市住宅建筑的节能设计提供一定的参考依据。     

Development of a testing method for control HVAC systems by emulation

CEN TC247 has prepared draft standards for main types of room controllers. These standards include a performance testing procedure that was designed to facilitate the introduction on the market of innovative controllers (adaptive controllers, fuzzy controllers …). The test procedure is based on the connection of the real controller to be tested to a virtual building and technical plants. The objective of the study which is part of the European SIMTEST project is the development of a testing method by emulation for control systems for heating ventilating and air conditioning applications. This study was focused on the development of numerical models of building and HVAC systems, which are the core of the test facility. The models developed are adapted to the needs of HVAC controller design and test. They take into account static and dynamic phenomena, which are necessary to assess, control functions in terms of comfort and energy consumption. These models are adapted to the test of all controllers, which are in the scope of the three draft standards CEN TC247, in particular to controllers for heating systems, fan coils, variable air volume systems and chilled ceilings. We present in this paper:

• (1)The testing method developed including the simulated environment with its models, the interfaces and the test procedure.
• (2)The validation of the testing method by inspection and comparison of the results obtained by emulation to the results obtained by real tests in a cell. Each application is tested with two different controllers: a high performance and low performance controllers. The same controllers are used in the two different testing methods.

     

ECOTECT能耗模拟下既有住宅建筑围护结构节能改造的热环境分析研究

目前,既有住宅建筑节能改造主要有围护结构改造和供热计量改造两方面。围护结构节能改造主要包括:外墙节能改造、外窗节能改造、屋面节能改造等技术措施的研究;建筑物围护结构节能改造除了能够降低建筑能耗之外,对建筑物室内热环境也有很大影响。采用ECOTECT能耗模拟软件,对西安市某住宅建筑围护结构不同节能改造方案的热环境进行模拟,深入分析不同节能改造方案的能源消耗、不舒适度、围护结构得热、温度分布和热舒适度情况,以热舒适为前提、节能为目的选择最优的节能改造方案。为既有住宅建筑节能改造方案优选提供依据。     

Assessing the total energy impact of manual and optimized blind control in combination with different lighting schedules in a building simulation environment

In this work, we investigated the interplay and the influence of lighting and blind control models on the heating, cooling, and lighting energy loads of an office room. By including different stochastic models for occupancy and appliances, we built a complete simulation environment based on the building simulation program IDA ICE. For control models, we implemented different strategies, including a simple on/off scheme, a realistic model of occupants, and an optimized control. In literature, the results are often compared with simple on/off schemes, which are not hard to beat in terms of performance. With an optimal control, the real saving potential is assessed, which can be used as benchmark case for comparison with other control models. Results based on annual simulations show that active occupants can reduce energy consumption by up to 50% from a worst-case scenario, whereas advanced controllers can further reduce the consumption by another 60%.     

降低建筑空调能耗研究

在分析贵阳市气候特点及实例建筑空调负荷特性的基础上,采用建筑环境模拟软件DeST对实例建筑室内基础室温以及全年建筑冷热负荷进行模拟,在分析模拟结果的基础上,结合贵阳市气候特点,提出如下三条贵阳市降低建筑空调能耗建议：1)舒适性空调设计应首先满足冬季采暖,然后考虑夏季制冷;2)自然通风是夏季降温的优先考虑方式,过渡季节调节是降低建筑制冷能耗的重要手段;3)增加围护结构保温和控制窗墙比是降低建筑采暖能耗的首要手段。研究结果不但能对贵阳市的建筑节能提供参考,而且还对广大温和地区建筑节能有参考意义。     

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

The energy saving that can be achieved by applying advanced glazing to a typical high-rise residential building in Hong Kong was evaluated using the simulation software EnergyPlus. It was found that application of low-e glazing would lead to a reduction in cooling electricity use by up to 4.2%. The saving due to application of low-e reversible glazing would be up to 1.9%; double-clear glazing up to 3.7%; and clear plus low-e glazing up to 6.6%. The achievable saving would depend on orientation of building wings, and type and location of rooms. The analysis suggests that for the high-rise public housing blocks in Hong Kong, the use of expensive advanced glazing would not be economically viable from the point of view of saving in cooling energy cost.     

Environmental impact of dwellings in use: Maintenance of façade components

The use of dwellings contributes significantly to human-induced environmental burden in a number of ways, including energy consumption and the maintenance and replacement of building components. The present study deals with the maintenance and replacement of external doors and windows in a Dutch reference dwelling and describes how life cycle assessment (LCA) methodology can be applied to quantitatively assess the environmental impact of various maintenance scenarios for the façade components. First, the most effective way to reduce the negative environmental impact in this context is to replace existing single and double glazing with high efficiency double glazing, thereby reducing energy consumption for space heating. Second, the use of timber frames causes less environmental impact than PVC frames with a steel core. Third, extending the service life of building components decreases the input of material resources, production processes and the waste processing of building components during the service life of a dwelling, which is beneficial to the environment. Maintenance activities should only be performed when needed, keeping the building components in good condition while minimising the transportation movements of maintenance workers. Finally, protecting timber components with an alternative paint that contains less solvent does not lower the assessed environmental impact, but low-solvent paint may be preferred because of health aspects both for maintenance workers and occupants of the dwelling.