Active Control of Daylighting Features in Buildings

Abstract: Due to increasing awareness of the importance of energy efficiency, daylighting features such as light shelves are becoming more and more popular. A light shelf is a horizontal or inclined projection with a high reflectivity meant to increase the depth of daylight penetration into a room. Currently, a light shelf is treated as a passive design element. It is designed to maximize the average distribution of daylight during the operating hours of a building and its geometry is not adapted to the changing conditions during the day. This article discusses a methodology for the active control of light shelves. A light shelf system whose geometry can be adapted is presented. The control of this system is treated as a global optimization problem. Geometrical parameters of light shelves are computed in real time to minimize the energy required for artificial lighting. An example of an office building is taken to illustrate the hourly energy savings possible through active control. It is demonstrated that building automation and control have considerable potential for energy savings.     

A simplified procedure for determining indoor daylight illuminance using daylight coefficient concept

The first step in evaluating the visual performance and energy efficiency provided by daylight requires an accurate estimation of the amount of daylight entering a building. The actual daylight illuminance of a room is mainly influenced by the luminance levels and patterns of the sky in the direction of view of the window at that time. The daylight coefficient concept, which considers the changes in the luminance of the sky elements, offers a more effective way of computing indoor daylight illuminances. Recently, Kittler et al. have proposed a new range of 15 standard sky luminance distributions including the CIE (International Commission on Illumination) standard clear sky. Lately, these 15 sky luminance models have been adopted as the CIE Standard General Skies. This paper presents a graphical method to calculate interior illuminance for the CIE standard clear sky using the daylight coefficient approach. The simplified techniques in the form of a nomograph and Waldram diagram were established and described. The performance of the proposed approach was evaluated against the results obtained by an independent calculation approach and a computer simulation program. It was shown that the daylight illuminances estimated by our graphical tool were in reasonably good agreement with those produced from the other two methods. The findings provide building professionals and students a reliable and simple alternative that incorporates the daylight coefficient concept to estimate the interior daylight illuminance and assess daylighting performance.     

Toxicity characteristics of commercially manufactured insulation materials for building applications in Taiwan

The use of thermal insulation materials for building applications is a promising technique but further investigations are needed in this area in order to enhance fire prevention. An experimental study has been carried out to determine toxicity characteristics of commercially manufactured insulation materials, according to UK Naval Engineering standards 713 (NES-713) and colorimetric analysis. Four materials, covering organic foamy and inorganic materials of most of insulation materials used in Taiwan, have been chosen. The various colorimetric gas reaction tubes were used to measure toxic constituents and contents. Toxicity index (TI) was then calculated to evaluate the combustion characteristic of the specimens. The influences of toxic constituents and contents on the toxicity characteristic of testing materials were examined. It was found that significant differences existed between organic foamy and inorganic materials. The results showed that the organic foamy materials, polyethylene foam and polyurethane foam, which did not meet the requirements of the low fire hazard material and were unfavorable in the building’s fire prevention. Finally, it was also observed that the results promote the real knowledge of these insulation materials by using the quantitative analysis to explicate the toxicity chemicals and types and can be important references for fire hazard analysis and developing materials in the future.     

Attitudes of school children to daylight and fenestration

The behaviour and attitudes towards their visual environment of 350 primary school children were studied in 11 schools of varying design, with particular attention to factors associated with fenestration and daylight. The investigation included social factors, personality characteristics of the children and the varying visual characteristics of the buildings including photometric studies. A significant proportion of children choose to sit or work near windows, the chief factor being the amount of daylight. View out, view content and nature are important. The most popular children occupy favoured window places. Space and comfort both visual and thermal are important. Sex separation is natural.     

Evaluation of natural illumination and thermal comfort conditions in the Ribeirao Preto’s Technological Village

The results of post-occupancy surveys of the 11 different construction systems used in the dwellings of the Technological Village of Ribeirao Preto are analyzed. The analyses focus on evaluating the natural illumination and thermal comfort conditions in selected habitation units after 2 years of use. All systems were devised to provide living conditions to low-income families with low purchasing power and, most importantly, to disseminate construction technologies adapted to, and appropriate for, this specific region of the country. The results indicate that the methodology employed is not appropriate using only classical factors to assess the illumination conditions, i.e. illuminance level and daylight factor, for a direct quantification of the illumination. The isolated use of these factors can result in distortions. The evaluation of the environmental conditions is relevant to observe that there can be differences between theoretical thermo-physical properties and actual features of the materials and construction systems analyzed.     

Life cycle assessment in buildings: State-of-the-art and simplified LCA methodology as a complement for building certification

The paper presents the state-of-the-art regarding the application of life cycle assessment (LCA) in the building sector, providing a list of existing tools, drivers and barriers, potential users and purposes of LCA studies in this sector. It also proposes a simplified LCA methodology and applies this to a case study focused on Spain. The thermal simulation tools considered in the Spanish building energy certification standards are analysed and complemented with a simplified LCA methodology for evaluating the impact of certain improvements to the building design. The simplified approach proposed allows global comparisons between the embodied energy and emissions of the building materials and the energy consumption and associated emissions at the use stage.The results reveal that embodied energy can represent more than 30% of the primary energy requirement during the life span of a single house of 222 m² with a garage for one car. The contribution of the building materials decreases if the house does not include a parking area, since this increases the heated surface percentage. Usually the top cause of energy consumption in residential building is heating, but the second is the building materials, which can represent more than 60% of the heating consumption.     

A study of the daylighting performance and energy use in heavily obstructed residential buildings via computer simulation techniques

The quality and quantity of natural light entering a building depends on both internal and external factors. In Hong Kong, many buildings are high-rise blocks constructed close to each other and hence the external factor plays a significant role in daylighting designs. This paper studies the daylighting performance and energy use for residential flats facing large sky obstructions via computer simulations. Key building parameters affecting daylighting designs are presented. The daylighting performance for typical interior rooms was investigated in terms of illuminance level and daylight factor. The daylight levels of residential flats can be severely reduced by neighboring buildings and hence the externally reflected component would be the main source of natural light. The indoor daylight levels for kitchen and living/dining faced large neighboring building were found always less than the standard maintenance illuminance during daytime period. These imply that many residential flats in Hong Kong would have to rely on supplementary electric lighting.     

Useful daylight illuminances: A replacement for daylight factors

This paper describes the application of a new paradigm, called useful daylight illuminance (UDI), to assess daylight in buildings. The UDI paradigm is designed to aid the interpretation of climate-based analyses of daylight illuminance levels that are founded on hourly meteorological data for a period of a full year. Unlike the conventional daylight factor approach, a climate-based analysis employs realistic, time-varying sky and sun conditions and predicts hourly levels of absolute daylight illuminance. The conventional approach produces a single number – the daylight factor as a percentage – for each evaluation point in the space. In contrast, a climate-based analysis results in an illuminance prediction for every daylight hour of the year for each point considered. The UDI paradigm offers a way to reduce the voluminous time-series data to a form that is of comparative interpretative simplicity to the daylight factor method, but which nevertheless preserves a great deal of the significant information content of the illuminance time-series. The UDI paradigm informs not only on useful levels of daylight illuminance, but also on the propensity for excessive levels of daylight that are associated with occupant discomfort and unwanted solar gain. In a conventional analysis of daylight provision and solar penetration, the two phenomena are assessed independently using methods that are idealised (daylight factor) and qualitative (shadow patterns). The UDI paradigm offers a simple methodology whereby daylight provision and levels of solar exposure are quantified using a single evaluative schema. Thus, it is also well-suited for teaching purposes. Application of the UDI paradigm is demonstrated using an analysis of design variants for a deep-plan building with a light-well. Comparison is made with the conventional daylight factor approach, the LEED daylight credit and measures of daylight autonomy.     

Development of a substitutive light source for indoor daylight calculations

The central focus of the paper is to present the results of the last 2 years of the research work on development of a substitutive light source for daylight calculation of the illuminance indoors. In the paper, calculation of spatial distribution of daylight according to the new CIE standard is discussed. Another focal topic is the calculation of photometric data of a light source which substitutes vertical window or vertical window opening in computer calculations. Through the development of photometric data for a light source, so that it can be imported into calculation software, this software becomes more powerful and useful.     

基于天然采光性能的建筑中庭形体设计导则研究

建筑师在进行形体创作时须将良好的技术性能作为重要目标，而直观、形象、非严格定量的设计导则是一种简易有效的辅助手段。然而，运用数字设计方法辅助建筑形体创作中的技术性能问题的既有研究对设计导则的关注较少，不能满足形体创作需求。本研究结合参数化模型、性能模拟等数字方法，以中庭为例、探讨了基于天然采光性能的圆形与方形中庭形体设计导则。研究结果表明，中庭的面积、贯穿层数、平面比例等形体参数对其天然采光性能具有显著影响，故在形体创作中建筑师应结合设计导则将天然采光性能纳入考虑；此外，本研究所采用的技术路线能够揭示建筑的技术性能与其形体特征的关系、是一种有效的设计导则获取方法。     

Performance of wall-stud cold-formed shear panels under monotonic and cyclic loading: Part I: Experimental research

The ever-increasing need for housing generated the search for new and innovative building methods to increase speed, efficiency and enhance quality, one direction being the use of light thin steel profiles as load bearing elements and different materials for cladding. The same methodology can be employed to build small steel structures for offices, schools or other purposes. Earthquake behaviour of these structures is influenced, together with other parameters, by the hysteretic characteristics of the shear wall panels. Results of a full-scale shear test programme on wall panels are presented, together with some numerical results concerning expectable earthquake performance of this structural typology.     

温度对多孔建材中VOC扩散系数的影响研究

已有研究表明,吸附特性与材料结构、挥发性有机化合物(Volatike Organic Compounds,VOCs)自身的物理化学特性、吸附材料填料率、室内污染源强度、室外污染源强度及环境温湿度等参数有关.但在实际应用中,除了这些不稳定或不确定的因素之外,是否存在其它影响因素还有待确定.本文通过理论与模拟分析,找出了通风是实际条件下是否考虑VOC吸附影响的关键因素,并结合算例提出了考虑和忽略建材吸附量影响的通风临界值的确定方法.分析可知,当换气次数小于0.1次/h时,要考虑地毯和沙发等吸附性较强材料的吸附影响;当换气次数大于20次/h时,可忽略其吸附影响.本文结论为综合考虑散发、吸附、传播和暴露规律的室内空气品质(Indoor Air Quality,IAQ)应用软件的开发提供了一定参考.     

Parametermodell zur Bestimmung des direkten Anteils des Tageslichtquotienten in Räumen mit Oberlichtern

Parameter model for determining the direct component of the daylight coefficient in spaces with roof lights This paper describes a parameter model for the calculation of the direct component of the daylight coefficient in spaces with polygonal windows (radiant surfaces) transmitting diffuse light. The model can be used to optimise the parameters described below in terms of the value and uniformity of the illuminance within the space without the need to use sophisticated raytracing models. The fundamental lighting parameters used as a basis for the calculation are explained, followed by the development of a differential equation based on the photometric distance law that describes the ratio of the illuminance on the outside of the radiant surface and the illuminance on the receiving surface. For the special case of a rectangular radiant surface, the tilt of the radiant surface is considered by rotating the coordinate system in one of the principal axes and appropriate adaptation of the integration limits. The equations can then be used to derive the ratio between the external horizontal illuminance and the illuminance on the tilted surface, and hence the direct component of the daylight coefficient. A space can be analysed by carrying out the calculation for a grid, from which minimum, maximum and uniformity values can be derived. The procedure is further simplified by a sky light diagram, which can be used to determine the direct component of the daylight coefficient at individual points.     

Conflicts in passive building performance: Retrofit and regulation of informal neighbourhoods

Urbanization growth in developing countries raises concerns regarding these countries' ability to consider slums, underdeveloped communities, and neighbourhoods in economic, health, and climatic goals. This research proposes a methodology that integrates algorithmic design and analysis strategies to define, study, and measure key parameters that affect the rehabilitation of these areas. Construction scenarios and design dimensions are analysed to establish design and comfort thresholds, and alternatives are simulated and tested to identify possible improvements. The methodology includes an optimisation step integrated in the workflow that maximizes thermal comfort, minimizes costs, and ensures fairness in the rehabilitation of large sets of buildings. This step identifies improvements in thermal comfort for different construction scenarios from which a two-staged rehabilitation plan is defined. The first stage comprises a sensitivity analysis to identify building materials regarding their improvement and cost of application, and the second defines the most suitable construction scenarios considering the results from the optimisation process for each building. Additionally, we research and document guidelines regarding the parameters tested for building design, revealing the existing conflicts between performance objectives, and the architect's role in their prioritization.     

评价建筑遮阳热舒适和视觉舒适重要参数试验——《建筑遮阳热舒适、视觉舒适性能检测方法》标准试验分析

本文主要介绍了评价建筑遮阳热舒适和视觉舒适若干参数的试验,着重对基本光学参数、厚样品反射比、目光利用性能及不透光度的测试和检测进行了深入的研究和分析测试结果。同时文中还对不透光度设备的设计、研制、检测过程及结果进行了介绍。,     

夏热冬冷地区办公建筑自然采光效果模拟分析

选取夏热冬冷地区苏州市某办公建筑作为模拟对象,采用Ecotect结合Radiance软件模拟建筑内自然采光情况,计算建筑内各楼层的平均自然采光系数与全自然采光百分比,分析玻璃可见光透射比、窗墙比对建筑自然采光效果和照明能耗节约量的影响。研究表明,采用可见光透射比较高的玻璃,适当增加建筑外窗面积,有助于提高建筑采光系数,改善自然采光环境,节约建筑照明能耗。     

An analysis of daylighting performance for office buildings in Hong Kong

Daylighting has often been recognized as a useful source of energy savings and visual comforts in buildings. Occupants expect good daylight in their working spaces. The quality and quantity of natural light entering a building depend on both internal and external factors. In Hong Kong, commercial building accounts for the major building energy use and electric lighting is one of the major electricity-consuming items. This paper studies the daylighting performance and energy implications for office buildings. A total of 35 commercial buildings have been selected in the survey. Key building parameters affecting daylighting designs are presented. Two typical office blocks were further analysed based on a lighting simulation program. The daylighting performance was evaluated in terms of daylight factor, room depth and glare index. It has been found that the daylighting performance for office buildings is quite effective. About one-third of the office areas that are near the perimeter regions have an average daylight factor of 5%. For inner region of deep plan offices, some innovative daylighting systems such as light redirecting panels and light pipe could be used to improve the daylighting performance. In general, the office building envelop designs are conducive to effective daylighting and proper daylight linked lighting controls could save over 25% of the total electric lighting use.     

Effectiveness of daylighting design and occupant visual satisfaction in a LEED Gold laboratory building

Using daylight as primary light source has been widely recognized as an important strategy to reduce building energy demand and enhance indoor environment quality. However, to design and operate a building to make full use of daylight, which is a dynamic light source, to meet diverse occupant needs remains a challenge. This paper reports a post-occupancy study of the visual environment in a laboratory building on a university campus, and puts a spotlight on the building occupants as it examines the effectiveness of the daylighting design and systems integration in creating a visual environment to support occupant comfort and satisfaction while reducing artificial lighting demand. Results show generally high satisfaction with daylit work environment and positive effect of the horizontal shading strategy. Issues about the integration between daylighting and electric lighting systems and level of occupant control are identified and discussed for improving the effectiveness of daylighting and enhancing the quality of the visual environment in the building of study. A multiple-tool methodology is developed and tested, which included occupant surveys, interviews, illuminance measurements, continuous data loggers, fisheye-lens camera and glare-identifying software, and documentation of spatial settings, systems features, and user behavior.     

Robustness of a methodology for estimating hourly energy consumption of buildings using monthly utility bills

The evaluation of building energy consumption under typical meteorological conditions requires building energy profiles on an hourly basis. Computer simulations can be used to obtain this information, but generating simulations requires a significant amount of experience, time, and effort to enter detailed building parameters. This paper considers a simple methodology for using existing EnergyPlus benchmark building energy profiles to estimate the energy profiles of buildings with similar characteristics to a given benchmark model. The method utilizes the building monthly energy bills to scale a given benchmark building energy profile to approximate the real building energy profile. In particular, this study examines the robustness of the methodology considered with respect to the parameter discrepancies between a given building and the corresponding EnergyPlus benchmark model used to estimate its profile. Test buildings are defined by perturbing several combinations of the parameters defined in the benchmark building model. The test buildings examined are similar to the EnergyPlus, medium sized office, benchmark building in Baltimore, MD, and a total of 72 distinct test building configurations are examined. The analysis reveals that the methodology can significantly reduce the errors introduced by discrepancies from the EnergyPlus benchmark model.     

Lichttechnisches und energetisches Verhalten von Fassaden moderner Verwaltungsbauten – Teil 1: Lichttechnisches Verhalten

Daylight and thermal energy performance of facades in office buildings, Part 1: Daylight performance. Regarding the impact on indoor illumination facade systems have to provide an appropriate visual indoor environment. In addition daylight penetrating the room through the facades should favourably influence the overall building energy balance. Daylight utilization can directly reduce energy consumption for electric lighting and can indirectly – due to the higher luminous efficacy of daylight compared to commonly used artificial lighting systems – reduce the thermal loads within the conditioned building spaces. In part 1 of this contribution the influence of different facade solutions on room illumination is systematically investigated by means of a parametric study of significant room, outdoor, environmental and climatic parameters for ten facade systems. The facade systems considered are conventional, permanently shaded, and light redirecting systems. The analysis of system performance is based on newly developed characteristics which allow the analysis and optimization of different facade systems under working conditions. Part 2 of the contribution shows the energetic interaction of the facade dependent internal loads by artificial lighting system and solar heat gains.