Indoor thermal environmental conditions near glazed facades with shading devices – Part I: Experiments and building thermal model

This paper presents an experimental study of indoor thermal environment near a full-scale glass facade with different types of shading devices under varying climatic conditions in winter. Interior glazing and shading temperature, operative temperature and radiant temperature asymmetry were measured for façade sections with roller shades and venetian blinds at different positions. Interior glass surface temperatures can be high during sunny days with low outdoor temperature. Shading systems significantly improved operative temperature and radiant temperature asymmetry during cold sunny days, depending on their properties and tilt angle. During cloudy days the impact was smaller, however the shading layers could still decrease the amount of heat loss through the façade. A transient building thermal model, which also calculates indoor environmental indices under the presence of solar radiation, was developed and compared with the experimental measurements. Part II of this paper uses this validated model with a transient, two-node thermal comfort model (including transmitted solar radiation) for assessment of indoor environmental conditions with different building envelope and shading properties, façade location and orientation.     

Evaluation of radiance's genBSDF capability to assess solar bidirectional properties of complex fenestration systems

Complex fenestration systems (CFS) need to be evaluated to quantify how well they contribute to avoid glare and manage the solar heat gains through building façades. It is possible to use solar bidirectional properties of CFS in some building energy simulations tools in order to evaluate more accurately their impact on lighting, cooling and heating energy consumption. genBSDF is a Radiance's program whose capabilities of assessing the bidirectional solar properties of CFS are evaluated in this paper. This evaluation was carried out for 16 cases of a venetian blind varying the solar properties and slope angle of the slats. Results of directional and bidirectional solar properties obtained by genBSDF with radiosity assumptions were compared with the results of the radiosity-based WINDOW algorithm. Results show an excellent agreement between the two approaches which demonstrates that genBSDF is a very precise and robust tool for assessing the solar bidirectional properties of CFS.     

Multi-criteria analysis for the integrated performance assessment of complex fenestration systems

Complex fenestration systems (CFS) designed to collect and redirect daylight from the sky-vault are generally placed on the upper part of a window in order to improve the distribution of indoor daylight. Due to their additional function as solar protection, their use might contribute to the mitigation of the unfavourable effects that the admission of daylight signifies, especially in buildings located in prevailing sunny climates (risk of glare and overheating). An appropriate selection of the CFS that better contributes to improve the interior daylight environment would imply an integrated performance assessment taking into account relevant aspects such as indoor daylight distribution and the visual and thermal comfort of occupants. However, such an assessment implies the use of performance criteria with different targets; therefore, in order to evaluate their overall performance, a multi-criteria analysis is applied in this study. The method presented here describes a comprehensive evaluation to determine those CFS that better contribute to an improved indoor daylighting environment in a building located in a prevailing sunny climate. The CFS performance assessment was undertaken with computer simulations using their bi-directional transmission distribution function (BTDF).     

碳纤维布粘贴加固BFRP筋-ECC-混凝土组合梁受弯性能研究

工程结构服役期间经常由于使用功能改变或使用荷载增加而需要对结构进行加固改造。为研究经碳纤维布粘贴加固后的玄武岩纤维增强塑料（BFRP）筋-工程用水泥基复合材料（ECC）-混凝土组合梁的受弯性能,对3组共12根不同ECC高度替换率（0、0.29和0.58）的BFRP筋-ECC-混凝土组合梁底分别粘贴1、2和3层碳纤维布的加固构件及未加固构件进行静力受弯性能试验。研究碳纤维布粘贴层数和ECC高度替换率对组合梁受弯承载力和破坏形态的影响。试验结果表明：采用受拉性能优异的ECC替代受拉区部分混凝土形成的ECC-混凝土组合梁不仅可提高构件承载力,还可有效改善构件抵抗开裂和变形的能力;组合梁底粘贴3层碳纤维布,裂缝宽度可降至未加固试件的10%,受弯承载力提高20%,挠度降低50%。借鉴钢筋混凝土理论,基于合理的基本假定和简化的材料本构模型,提出粘贴碳纤维布加固的组合梁受弯承载力计算式,并给出碳纤维布强度折减系数,理论预测值与试验实测值吻合良好。     

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.     

Performance analysis of external shading devices

The performance of the basic vertical and horizontal types of external shading devices was studied in detail. The different performance modes are presented in the form of shading masks featured by the cutoff angles.

Mathematical formulae were derived to express the cutoff angles in terms of the various geometrical parameters characterizing the combination of the shading device and the fenestration. These angles define the partial and complete shading phases. The formulae are put in generalized forms, in terms of normalized geometrical ratios, so as to be independent of the absolute dimensions. A unified approach was followed for both vertical and horizontal devices so that the derived normalized expressions can be adopted for the two types.

The effect of the various geometrical factors on the cutoff angles, i.e. on the form of the shading mask, was investigated for different configurations of vertical and horizontal shades. Based on the derived relations, the trends of variation, of the cutoff angles with these factors, are graphically presented for each case.     

The impact of increasing the building envelope insulation upon the risk of overheating in summer and an increased energy consumption

This work describes a study aiming to establish the impact of the increase of the building envelope insulation upon the thermal performance of buildings. A particular emphasis is placed upon the consequences in terms of higher temperatures in summer, potentially leading to increased needs for installation of air-conditioning. This study also describes the coupled influence of other parameters that can reduce overheating, like solar shading and ventilation. The methodology is based on parametric studies obtained through simulations. The comfort analysis methodology is based on the adaptive approach. The results show that, with added insulation, it is necessary to control solar and internal gains more closely to avoid overheating in summer. Results also include the requirements to avoid air-conditioning, in terms of window shading for each level of insulation and internal gains.     

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.     

Shading performance of a vertical deciduous climbing plant canopy

Deciduous climbing plant canopies strategically integrated to building façades can act as dynamic solar shading devices responsive to the seasonal climatic changes. Maximum shading occurs in the summer when the plant is at its peak growth. The shedding of leaves in autumn and winter reduces the shading and allows beneficial solar radiation to be absorbed by the opaque surface of the building façade or penetrated through the windows to the building interior. Although climbing plants have long been used for moderating the microclimate of buildings, there are very few scientific investigations to quantify such effects. This paper reports the findings of a study with specific focus on the shading performance of a vertical deciduous climbing plant canopy. It justifies the selection of Virginia Creeper as an appropriate plant for growth in the UK climate and describes the planting, monitoring and analysis procedures adopted to determine a proposed dynamic Bioshading Coefficient Function – which is used to represent the shading performance of the climbing plant canopy over its annual growing and wilting cycle. A thermal model was developed which identified the key parameters required for establishing the Bioshading Coefficients. Two climbing plant canopies (referred to as Bioshaders) were set up in an existing building in Southeast UK and monitored for 2 years. Measured data were used to calculate a series of daily Bioshading Coefficients which were subsequently applied to establish the Bioshading Coefficient Function. The research also identified issues affecting the indoor environment as a result of the application of Bioshaders.     

Ductile moment-resisting frames using cold-formed steel sections: An analytical investigation

This paper presents an investigation on the potential use of cold-formed steel sections (CFS sections) in moment-resisting frames (MRFs) for seismic applications. The main limitation of CFS sections is the low out-of-plane stiffness of their thin-walled elements which leads to low ductility. The main components of MRFs are beams, beam-column connections and columns. In earthquake resistant MRFs, the beams are designed to provide considerable ductility, whereas the other elements are mainly limited to their elastic range. The performance of a new shape of CFS beam with curved flange is examined analytically and compared with that of conventional shapes. The proposed beam-column connections include through plates which potentially limit the out-of-plane action of the forces transferred through the connections. The behaviour of both individual CFS beam sections and CFS beam-column connections is studied by means of finite element analysis (FEA). The results of the analyses show that the new beam cross sections and connections exhibit a good ductile behaviour, something which cannot be achieved by conventional cold-formed frame elements.     

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...     

Evaluating the performance of shading devices and glazing types to promote energy efficiency of residential buildings

This study presents a novel residential envelope transmittance value (RETV) performance-based approach for determining the suitable external shading devices and glazing types to improve energy efficiency in residential buildings. The approach is applied to two residential buildings types, namely, point block and slab block, for any given orientation in an entire year. In this approach, a RETV equation for residential buildings was first developed. Employing this equation, we demonstrated how the design of shading devices and the selection of glazing type impact the cooling load of high-rise residential buildings. Comparing results from the model simulations, the half egg-crate louver was found to be the most suitable shading device for residential buildings facing the north and south orientations, whereas a horizontal projection with 30° downward tilt was appropriate for facade facing the east and west orientations to reduce cooling load. In addition, simulations also indicated low-E single clear glazing to be a suitable glazing since it results in relatively economical short payback periods.     

Numerical simulation of passive and active solar strategies in buildings with complex topology

In this paper a numerical software, that simulates the building thermal behaviour with complex topology in transient conditions, was developed and used in the study of kindergarten thermal response and the occupants’ thermal comfort and air quality in Mediterranean conditions. In this numerical model a new building three-dimensional grid generation philosophy, closer to the reality, that considers the building and the surrounding buildings used in the long and short-wave calculus, the external and internal shading devices, the energy and mass balance integral equations philosophy generated by the building geometry, the equation system resolution done by the Runge-Kutta-Felberg with error control and the human thermal comfort level evaluated through human thermo-physiology, are developed. In the simulation, with a real occupation cycle, the compartments, the building opaque bodies, the building transparent bodies, and the external shading devices were considered. In passive strategies the kindergarten is equipped with multiple inclined aluminium shading devices placed above the transparent windows level and in front to the transparent door facing south, removable inclined tissue shading devices placed in front to the transparent windows facing east, and horizontal fabrics shading devices placed above the transparent panel levels facing south, south-west and west. In this study, made with natural and forced ventilation, the summer and winter conditions were used. In summer conditions, the forced ventilation active strategies in all spaces with cold air from the external environment during the night, and in occupied spaces with stored cold air from the underground space were used. In winter conditions forced ventilation from an internal greenhouse, to heat the internal occupied cold spaces, was used.     

GlareShade: a visual comfort-based approach to occupant-centric shading systems

This paper presents a novel method for designing of an occupant-centric shading algorithm that utilizes visual comfort metric as the form-generating criteria. Based on the premise of previous studies that demonstrate glare as the most important factor for operating shading devices, GlareShade is introduced as a simulation-based shading methodology driven by occupant's visual comfort. GlareShade not only responds to changing outdoor conditions such as the movement of the sun and the variation of cloud cover, but it also accounts for building specific local conditions. GlareShade draws its strength and flexibility from an occupant-centric approach that is based on the visual field of view of each occupant as the occupant is performing common visual tasks in a given environment, and the developed shading system is linked to a distributed sensing network of multiple occupants. ShadeFan is demonstrated as a proof-of-concept dynamic shading system utilizing the GlareShade method.     

Thermal performance of bedrooms in a multi-storey residential building in southern Brazil

This paper presents a methodology used to compare the thermal performance of bedrooms in a multi-storey residential building located in Florianópolis, southern Brazil. Air temperature was recorded over a 29-day period in eight unoccupied bedrooms located on two floors and four orientations. The assessment involved the measurement of absorptance of the colour of external surfaces, calculation of thermal properties of walls and windows, drawing of shading on the windows, correlation between external and internal temperatures, and correlation between temperature differences and thermal properties. The main conclusion that can be made from the research is that U-value and façade area are the two variables that show the best correlation with maximum air temperatures and therefore should be minimised in order to improve thermal conditions over summer; and that thermal capacity and thermal time lag are the two variables that show the best correlation with minimum air temperatures and should be maximised to improve thermal conditions over winter.     

Furnace tests on unprotected and protected concrete filled structural hollow sections

The accurate prediction of cross-sectional temperatures within concrete filled steel hollow (CFS) sections is critical for the accurate prediction of fire resistance. Whilst there have been many thermal and structural tests conducted on CFS columns, there are few that report the full cross-sectional thermal profile, and when they are reported, the sensor density is low, hindering the ability to validate models. This paper presents furnace tests and thermal modelling on 14 unprotected and 20 protected CFS sections, and examines the effect of several parameters on cross-sectional thermal profiles, as well as assessing the accuracy of both Eurocode thermal analysis guidance and intumescent fire protection design guidance. This paper shows that; (a) the assumptions within the Eurocode guidance can lead to large over-estimations in cross-sectional temperatures; (b) proposes new thermal modelling assumptions in three key areas; and (c) shows that the current intumescent fire protection design guidance is very conservative.     

A personalized measure of thermal comfort for building controls

A personalized measure for thermal comfort has been applied for use in combination with smart controls for building automation. Using data from a field study, we first show the superiority of personalized measures for thermal comfort compared to standard non-adaptive methods. Based on this knowledge we describe a methodology, using logistic regression techniques, to convert user votes to a probability of comfort. We also describe the interface used to collect the votes. We show that, for a given subject, our thermal profile converges against the probabilities found in the field study. As a case study we implemented the measure in a control algorithm to control the shading devices. The results clarify the mode of action and also show the effectiveness of the method.     

A software framework for model predictive control with GenOpt

There is a growing interest in integrated control strategies for building systems with numerous responsive elements, such as solar shading devices, thermal storage and hybrid ventilation systems, both for energy efficiency and for demand response. Model predictive control is a promising way of approaching this challenge. This paper presents a flexible software framework for model predictive control using GenOpt, along with a modified genetic algorithm developed for use within it, and applies it to a case study of demand response by zone temperature ramping in an office space. Various areas for further research and development using this framework are discussed.