Thermal behaviour of a ventilated double skin facade in hot arid climate

Modern Movement in architecture has resulted in a large number of high-rise buildings with glazed facades which increase the energy load of the buildings. To combat this phenomenon in colder climates, architects have turned to using double skin facades. These facades comprise of: a completely transparent external facade; an internal skin; and an air layer between the two. Research on the performance of double skin facades mostly considers cold and moderate climates. In addition, data collection is normally based on simulations, rather than actual field measurements. In this paper a building with double skin facade was monitored for 2 weeks in summer and 2 weeks in winter in the hot arid climate of Iran, in order to observe the behaviour of the facade both in hot and cold conditions. Additionally, simulations were performed on the case study building with and without double skin facade, to assess the effectiveness of the facade. The results revealed that the temperature difference between the outer skin, the inner skin and the cavity can significantly save heating energy in winter. To reduce the cooling loads in summer it is essential to introduce additional techniques such as night ventilation and installation of shading devices for the cavity.     

Thermal characteristics of a double-glazed external wall system with roll screen in cooling season

A double-skin system (double-glazed external wall) is an effective passive system that can be used to decrease solar heat gain into buildings. Detailed information on the thermal distribution of double-skin facades is necessary to design better systems that can provide thermal comfort and conserve energy. In this study, the three-dimensional thermal characteristics of double-skin facades that had the ventilation opening installed partially and were screened partially by the adjacent buildings were investigated by field measurements. To that end, field measurements were carried out on the double-skin exterior wall (9.4 m high and 27.0 m wide) installed in an atrium located in the west of an existing building during cooling period for typical summer conditions. Maximum air change rate of natural ventilation through the bottom opening up to the top opening is about 20–25 [1/h], the reduction ratio of total solar heat gain compared with those of non-natural ventilation is about 25%. The exhaust solar heat gain is about 100 W/m² per inner glass surface area of the double-skin facades. Air temperature distribution of air space in the double skin was ranged from 30 °C to 44 °C, and heat gain difference ranged from 50 W/m² to 130 W/m². The influence of the ventilation openings and the shade conditions on temperature distribution of double skin is found to be significant and the double-skin system was verified to reduce the cooling loads effectively.     

Heating and cooling in high-rise buildings using facade-integrated transparent solar thermal collector systems

New facades of high-rise buildings often include renewable energy converters to allow “green building” operation. At the same time, numerous tenants value visual transparency. Transparent solar thermal collectors (TSTCs) aim at decreasing the non-renewable primary energy demand and increasing the visual transparency at the same time. On the one hand, this paper presents the main modelling challenges that arise when considering building facades and especially integrated TSTC systems. New transient systems simulation (TRNSYS) [Beckman, W. A., L. Broman, A. Fiksel, S. A. Klein, E. Lindberg, M. Schuler, and J. Thornton. 1994. “TRNSYS The Most Complete Solar Energy System Modelling and Simulation Software.” Renewable Energy 5 (1–4): 486–488] types have been especially developed for this purpose. A simplified model is presented for comparison purposes. On the other hand, the overall performance for a building with facade-integrated TSTC, as measured by its non-renewable primary energy demand, is treated. This is achieved by considering a complete simulation model coupling the TSTC, building and heating, ventilation and air conditioning operation. Possibilities for primary energy savings are investigated using the building mass as additional thermal storage.     

带天井高层住宅建筑热环境试验和分析

为研究带天井的高层住宅建筑的热环境现状以及更好地利用天井的自然通风来改善建筑内的热环境,采用实测和问卷调查相结合的方法,对长沙市的一栋带天井的高层住宅建筑进行了热性能试验和分析。在不同的夏日天气状况下,该建筑物居住区房间的平均温度和走廊的平均温度都比室外平均温度低,天井的自然通风在夏季对其周围空间具有良好的降温效果。     

The influence of the wind-blocking effect by a building on its wind-driven rain exposure

Wind-Driven Rain (WDR) is one of the most important moisture sources that affect the hygrothermal performance and the durability of building facades. The complexity of WDR has led to the use of Computational Fluid Dynamics (CFD) to predict the amount of WDR falling onto building facades. Recently, the CFD model for WDR simulation has been successfully validated for a low-rise building of complex geometry and for a range of rain events, providing confidence for further numerical studies. In this paper, the influence of the wind-blocking effect by a building on its WDR exposure is examined. Part of the latest WDR CFD validation study for the VLIET building and CFD simulations of the WDR distribution on four different single-building configurations are presented. It is shown that the wind-blocking effect is one of the main factors that govern the WDR distribution pattern. As a result, high-rise buildings do not necessarily catch more WDR than low-rise buildings.     

A new type of double-skin façade configuration for the hot and humid climate

The performance of the double-skin façade depends closely on the chosen ventilation means within its intermediate space. The modes of ventilation could be natural (buoyancy driven), forced (mechanically driven) or mixed (both natural and forced). Oesterle et al. has attempted to classify the double-skin constructions into four different types, namely box window façade, shaft-box façade, corridor façade and multi-story façade. A number of interesting investigations and findings are reported in the literature pertaining to passive ventilation in buildings and the thermal performance of double-skin facades. The researches have revealed close link between natural ventilation design and the function of double-skin façade. Most of them are using the idea of stack effect or the solar chimney concept and found that passive ventilation in summer is possible even for multi-storey buildings. It was found that significant energy saving is possible if natural ventilation could be exploited through the use of double-skin façade. In this research, CFD was used to analyse various thermal comfort parameters with different double façade configurations to determine a new type of double-skin façade configurations which will provide a better indoor thermal comfort in the hot and humid climate through natural ventilation strategies for the high-rise buildings.     

The outdoor air ventilation rate in high-rise residences employing room air conditioners

Ventilation is important because it affects indoor environmental conditions, including air pollutant concentrations that may modify the health of the occupants of a building, or their perceptions and comfort. This paper reports, first of all, on field studies monitoring indoor overnight CO₂ levels and outdoor ventilation rates in bedrooms employing room air conditioners (RACs), so the current situation of ventilation in actual high-rise residential buildings in Hong Kong can be appreciated. This is followed by a report of the results of laboratory experiments where two typical RACs were used in an examination of outdoor air ventilation characteristics in rooms employing RACs. The results of field studies showed that the outdoor ventilation rates in the measured bedrooms equipped with RACs in high-rise residential buildings in Hong Kong could not meet the ventilation requirement specified in the ASHRAE standard 62-2001 even if there was only one occupant in a bedroom. Although the use of a window-type air conditioner (WRAC) may provide a higher outdoor ventilation rate than the use of a split-type air conditioner (SARC), this may be ascribed to the fact there is more natural infiltration when a WRAC is used. The ventilation damper currently available in a WRAC does not significantly affect the outdoor ventilation rate. Therefore, such a damper cannot be expected to provide the ventilation rate as required by a ventilation code and its intended function of controlling ventilation is limited. In addition, the air exhausted from indoors to outdoors through the ventilation outlet in a WRAC is air that has just been cooled by the cooling coil (evaporator). This is unreasonable, because exhausting just-cooled and dehumidified air is a waste of energy. Therefore, an improved design for a WRAC has been suggested. Finally, the outdoor ventilation requirement for bedrooms at nighttime, when occupants are asleep, is discussed. A new ventilation rate of 3.0 l/s per person for the sleeping environment in high-rise residential buildings is proposed.     

Is day natural ventilation still possible in office buildings with a double-skin façade?

Double-skin facades are assuming an ever-greater importance in modern building practices. But there are still relatively few buildings in which they have actually been realized, and there is still too little experience of their behaviour in operation.To preserve comfort and reduce cooling loads, it is important to apply natural cooling strategies.This article examines the efficiency of the natural day ventilation in relation to the double-skin orientation and the speed and orientation wind.     

Numerical study of the influences of different patterns of the building and green space on micro-scale outdoor thermal comfort and indoor natural ventilation

Citizens could enjoy a healthy and comfortable living environment if outdoor thermal comfort and sufficient natural ventilation are available in their dwellings. In this paper, numerical studies were performed with the Simulation Platform for Outdoor Thermal Environment (SPOTE) to investigate: (1) the thermal environment and pedestrian thermal comfort of the occupants in the open space with different patterns of the building and green space; (2) the wind pressures on the building facades and the natural ventilation rate of these buildings. The conclusions are summarized as follows: (1) it has been observed that the long facades of building and green space, which are parallel to the prevailing wind direction, can accelerate horizontal vortex airflow at the edges where such airflow could strengthen the convective exchange efficiency of hot air in low altitude and cold air in high altitude, and can obtain thermal comfort and sufficient natural ventilation at the pedestrian level; (2) after a series of simulations and comparisons, the configuration in which buildings are grouped in staggered layout with a centralized green space can provide better ventilation conditions and suitable air movement as a result of attenuated revised standard effective temperature (SET*). This configuration is regarded as the optimum pattern of the building and green space.     

Natural ventilation in a double-skin facade

Double-skin facades are assuming an ever-greater importance in modern building practice. There is an increasing demand for higher quality office buildings. Occupants and developers of office buildings ask for a healthy and stimulating working environment.Double-skin facades are appropriate when buildings are subject to great external noise and wind loads. A further area of application is in rehabilitation work, when existing facades cannot be renewed, or where this is not desirable. Double-skin facades have a special aesthetic of their own, and this can be exploited architecturally to great advantage.However, there are still relatively few buildings in which double-skin facades have actually been realized, and there is still too little experience of their behavior in operation.In this matter, we choose to study the natural ventilation in multi-storey double-skin facades. Simulations where realized with TAS software on a building proposed in the frame of the subtask A of the Task 27 (performance of solar facade components) of the International Energy Agency, Solar Heating and Cooling Program.We decide to study a sunny summer day; and we analyze the double-skin facade behavior for various conditions: impact of the double-skin orientation and impact of the wind orientation and the degree of wind protection.     

The impact of auxiliary energy on the efficiency of the heating and cooling system: Monitoring of low-energy buildings

This paper presents a detailed meta-analysis of end and primary energy use for heating, cooling and ventilation of 11 low-energy non-residential buildings and one residential building in Germany that belong to the EnOB research program launched by the German Federal Ministry for Economy. In particular, the analysis emphasizes the substantial impact of auxiliary energy use on the efficiency of heating and cooling performance. The investigated buildings employ environmental energy sources and sinks - such as the ground, ground water, rainwater and the ambient air - in combination with thermo-active building systems. These concepts are promising approaches for slashing the primary energy use of buildings without violating occupant thermal comfort. A limited primary energy use of about 100 kWh_prim/(m²_neta) as a target for the complete building service technology (HVAC and lighting) was postulated for all buildings presented. With respect to this premise, a comprehensive long-term monitoring in high time resolution was carried out over the course of two to five years, with an accompanying commissioning of the building performance. Measurements include the energy use for heating, cooling, and ventilation, as well as the auxiliary equipment, the performance of the environmental heat source and sink, and local climatic site conditions.     

超高层建筑机电设备的安装新技术分析

主要介绍了高层建筑机电设备安装新技术的特点,分析了高层建筑机电设备安装中存在的种种问题,提出了高层建筑机电设备安装技术的改进措施,最后介绍了超高层建筑机电设备的安装新技术,以促进机电设备安装质量的提高。     

Natural cooling strategies efficiency in an office building with a double-skin façade

In these last years, a great deal of interest has been devoted to double-skin façades due to the advantages claimed by this technology (in terms of energy saving in the cold season, high-tech image, protection from external noise and wind loads).The advent of computers and other office equipment increased the internal heat gains in most offices. Highly glazed façade become very common. This, together with the extra heat gains from the electric lighting made necessary by deep floor plans, and the wider use of false ceilings, increased the risk overheating.To preserve comfort and reduce cooling loads, it is important to apply natural cooling strategies.This article examines the efficiency of the various strategies in an office building with and without a double-skin façade during a sunny summer day. It mainly studies the natural night ventilation possibility in related to the double skin orientation and the speed and orientation wind.In this matter, we choose to study a multistory double-skin facades behavior. Simulations were realized with TAS software on the building proposed in the frame of the subtask A of the Task 27 (Performance of solar facade components) of the International Energy Agency, Solar Heating and Cooling Program.     

Ocular,nasal, dermal and respiratory symptoms in relation to heating,ventilation, energy conservation,and reconstruction of older multi-family houses

The aim was to study relationships between symptoms compatible with the sick building syndrome, type of heating and ventilation system, energy saving, and reconstruction in older dwellings. In Stockholm, 4815 inhabitants in 231 multi-family buildings built before 1961 were randomly selected, of whom 3241 participated (77%). Symptoms and personal factors were assessed by a postal questionnaire. Independent information on building characteristics, and energy saving measures was gathered from the building owners. Multiple logistic regression analysis was applied to calculate odds ratios (OR) adjusting for age, gender, hay fever, current smoking, population density, type of ventilation, type of heating system, and ownership of the building. Subjects in buildings with a mechanical ventilation system had less ocular and nasal symptoms (OR = 0.29-0.85). Heating by electric radiators, and wood heating was associated with an increase of most symptoms (OR = 1.18-1.74). In total, 48% lived in buildings that had gone through at least one type of reconstruction or energy saving remedies during the latest 10 years, including exchange of heating or ventilation system, and sealing measures (exchange of windows, sealing of window frames, roof/attic insulation, and phasade insulation). Energy saving was associated with both a decrease and increase of different symptoms. Major reconstruction of the interior of the building was associated with an increase of most symptoms (OR = 1.09-1.90), and buildings with more than one sealing measure had an increase of ocular, nasal symptoms, headache and tiredness (OR = 1.22-2.49). In conclusion, major reconstruction of the interior, direct heated electric radiators, wood heating, and multiple sealing of buildings were associated with an increase of some symptoms. The study supports the view that mechanical ventilation in dwellings is beneficial from a health point of view.     

CFD simulations of natural ventilation behaviour in high-rise buildings in regular and staggered arrangements at various spacings

Natural ventilation, which is in line with the concepts of sustainability and green energy, is widely acknowledged nowadays. Prevailing winds in urban areas are unavoidably modified by the increasing number of closely placed high-rise buildings that significantly modify the natural ventilation behaviour. This paper explores the effects of building interference on natural ventilation using computational fluid dynamics (CFD) techniques. The cross-ventilation rate (temporal-average volumetric airflow rate) of hypothetical apartments in a building cluster under isothermal conditions was examined using the standard two-equation k − ? turbulence model. The sensitivity of ventilation rate to wind direction, building separation and building disposition (building shift) was studied. Placing buildings farther away from one another substantially promoted the ventilation rate, cancelling the unfavourable interference eventually when the building separation was about five times the building width (the optimum separation). The characteristic flow pattern leading to this behaviour was revealed. With the adoption of building disposition, the optimum separation could be reduced to three times the building width. In addition, the airflow rates could be doubled with suitable shifts. Building disposition is therefore one of the feasible solutions to improve the natural ventilation performance in our crowded environment.     

Design for maintainability of high-rise vertical green facades

ABSTRACT

Since the introduction of vertical greenery systems (VGSs) in Singapore, building designers have experimented with different VGS designs and types to apply to high-rise building facades. Although innovative designs have brought variety to the utilitarian high-rise facades clad in glass, steel and concrete, little consideration has been given to the issues of maintainability during the design/planning stage. This lack of foresight and planning has hindered the efforts of maintenance personnel and compromised the performance of such green facades. To address these concerns, an instrumental case study approach was undertaken using a series of site investigations and interviews with experts and stakeholders. The aim of this research was to strengthen the knowledge base on high-rise vertical greenery facades in the tropics, leading to the formulation of case study-based ‘design for maintainability’ (DfM) guidelines. These guidelines will assist clients, designers and contractors by providing a supplemental reference during the design, installation and maintenance of high-rise VGSs located in tropical regions.     

迎世博600天既有建筑外墙检测及整修

为迎接上海市世博会的召开,增加上海市的城市魅力,特在迎世博600天之际,对上海市各区县的既有高层建筑外立面进行检测和综合改造。文章介绍采用红外热像法检测既有高层建筑外墙的方法和整修方法。     

高层公共建筑消防设施在灭火救援中的合理运用

随着我国经济发展,城市化进程在不断增速,其表现最为明显的就是高层建筑的发展。近些年,高层公共建筑的数量与密度在不断提高,这对于城市的发展无疑是有利的,但伴随的安全问题也不容忽视。高层公共建筑由于自身建筑高度高、体量大的特点,单纯依靠政府消防救援力量很难快速救助被困人员、控火、灭火,这就需要消防救援人员合理运用建筑内部消防设施,开展灭火救援工作。因此,文章通过分析现有高层公共建筑的火灾特点,结合建筑内部消防设施的设置,探讨在高层公共建筑灭火救援战斗中如何更好地做到固移结合,希望能对高层公共建筑的灭火救援工作起到一定作用。     

组合布局对建筑立面风驱雨分布影响特性的数值分析

风驱雨（Wind-Driven Rain,简称WDR）是建筑外立面最主要的水分来源,为外墙材料耐久性能及建筑温湿环境的重要影响因素。目前,WDR分布特性的研究主要针对单体建筑布局,考虑群体布局条件下建筑立面WDR分布以及受布局扰动影响的研究仍比较缺乏。基于欧拉多相流模型的WDR数值模拟方法,在验证方法对两建筑串列布局下较复杂WDR场具有较好模拟适用性的前提下,针对两建筑串列布局方式,考虑施扰建筑高度(h)及间距(d)变化,模拟不同工况下受扰建筑迎风面WDR分布,通过与单体布局情况进行比较,重点分析受扰建筑迎面风WDR分布特点及局部区域WDR变化规律,获取该布局变化时气动干扰对受扰建筑迎风面WDR分布的影响特性。结果表明：受扰建筑迎风面WDR分布受施扰建筑高度变化影响较大,受间距变化的影响相对较小,而局部区域干扰因子更能有效反映受扰建筑立面WDR分布的气动干扰影响。     

Naturally ventilated and mixed-mode buildings—Part I: Thermal modeling

Mixed-mode cooling strategies rely on several different means of delivering cooling to the occupied spaces of buildings. These different means, or modes, of cooling include different forms of natural ventilation through operable windows, ventilation assisted by low-power fans, and mechanical air conditioning. Control of mixed-mode cooling systems requires a thermal model tuned to accurately predict the dynamics of a specific building. This paper presents a flexible system-identification framework for linear thermal models that is well suited to accommodate the unique features of mixed-mode buildings. The effectiveness of this framework was demonstrated on a multi-zone, mixed-mode building, with model-prediction accuracy shown to exceed that published for other naturally ventilated or mixed-mode buildings, none of which exhibited the complexity of this building. A companion paper employs the thermal model in an efficient algorithm to optimize control strategies over extended planning horizons.