Window Shading Research Articles

Technoeconomic assessment of the impact of window shading retrofits on the heating and cooling energy consumption and GHG emissions of the Canadian housing stock

This study evaluates the economic feasibility and the effect of window shading retrofits on the heating and cooling energy requirement of the Canadian housing stock based on detailed energy simulations conducted using the Canadian Hybrid Residential End-Use Energy and GHG Emissions Model (CHREM).The study found that adding 1/2in. light aluminum VB on the indoor side of windows with automatic control based on zone temperature would result in substantial reduction in energy and GHG emissions in the Canadian housing stock. Other types of window shading devices may be effective in reducing the cooling energy consumption, but they result in an increase in overall energy consumption when both heating and cooling season performance is taken into consideration.The economic feasibility of VB depends largely on the fuel mix and cost of fuels used as well as the tolerable payback period and expected fuel cost escalation rate. Thus, the economic feasibility is different for each province.

The separation of monocular and binocular contrast

The contrast asynchrony is a stimulus configuration that illustrates the visual system's separable responses to luminance and luminance contrast information (Shapiro, 2008; Shapiro et al., 2004). When two disks, whose luminances modulate in phase with each other, are each surrounded by a disk, one light and one dark, observers can see both the in-phase brightness signals and the antiphase contrast signals and can separate the two. Here we present the results of experiments in which observers viewed a similar stimulus dichoptically. We report that no asynchrony is perceived when one eye is presented with modulating disks and the other eye is presented with the black and white surround rings, nor is an asynchrony perceived in gradient versions of the contrast asynchrony. We also explore the "window shade illusion" (Shapiro, Charles, & Shear-Heyman, 2005) dichoptically and find that when a modulating disk is presented to one eye and a horizontally split black/white annulus is presented to the other, observers perceive a "shading" motion up and down the disk. This shading can be seen in either direction in the binocular condition, but it is almost always seen as moving towards low contrast in the monocular condition. These findings indicate the presence of separable retinal and cortical networks for contrast processing at different temporal and spatial scales.

Cost-effective design solutions for low-rise residential Net ZEBs in Mediterranean climate

Today the concept of net zero-energy building (Net ZEB) is well-known and widespread in the scientific community. Nevertheless, how to effectively transfer this concept into the building market is not as much widespread, especially in Mediterranean regions.In this context, this paper aims at identifying a series of cost-effective technical solutions, supported also by construction details, which can be usefully adopted to define a standard for low-rise residential Net ZEBs in mild Mediterranean countries. The study refers to terraced housing, as it represents one of the most diffuse residential type currently built in southern Europe.The results show that with the suggested solutions – such as increased insulation, use of low-emissive glazing and window shadings, free-cooling through natural ventilation, solar thermal collectors for Domestic Hot Water – common terraced housing can significantly decrease the energy needs and reach the Net ZEB target by using only a limited amount of PV panels. Due to the diffusion of this building type, the technical solution here discussed can be extended to a significant portion of the real estate and effectively considered for the design of future residential Net ZEBs in Mediterranean countries.

An Assessment of Comfort Levels of Buildings with Shaded and Non-Shaded Windows in Warm Humid Climates

Thermal comfort problems experienced in buildings in warm humid climates has been a major concern for designers in the environmental design specialty especially in Nigeria and other developing countries. This paper through controlled experiments studies the effect of window shading on indoor comfort levels of buildings exposed to warm humid climates. Experimental model buildings with shaded and non-shaded windows were constructed for this purpose. Comfort data were obtained from the buildings and meteorological stations including comfort parametric ranges. The data were analyzed with statistical tools involving the central tendency and dispersion. Hypotheses were tested. Results showed that window shading has significant effect on the comfort level of buildings and consequently energy usage.

Multi-objective building energy consumption prediction and optimization for eco-community planning

The planning of an eco-city/community involves multiple factors, including building energy consumption, carbon emission, initial cost, as well as local natural, geographical and socio-economic conditions. To assist policymakers and planners to make the optimum decisions, especially in the early planning stage of an eco-city/community, this paper developed a quick and convenient multi-objective prediction and optimization tool. Building energy consumption, carbon emission and initial cost were considered as three sub-objectives. The optimization parameters include those for building envelope (i.e. heat transfer coefficient, window shading coefficient, unit cost) and those for air-conditioning system (i.e. coefficient of performance) for each type of buildings. The building energy consumption was calculated based on the BIN method. The carbon emission was determined with the energy consumption and carbon emission factor of each energy type. The initial incremental cost was calculated with the material and product price. Priority consideration of the three sub-objectives was achieved by weight factor method during the optimization process. The weight factors could be determined empirically by policymakers, investors, or planners. The optimization results can be referred by decision makers. Finally, an eco-community in Chongqing, China was taken for a case study, and parameter sensitive analysis was conducted.

The Sun-Shading Technologies of the Existing Traditional Dwellings in China

Shading space is an important characteristic of China's traditional architecture. The traditional dwellings in China are taken as the research object. On the basis of the statement of the classification and function of building shading, this paper focuses on the various shading methods such as eaves shading, function space shading, windows shading, courtyard shading, green shading and building mutual shading in the building layout.

The effect of window shading design on occupant use of blinds and electric lighting

Occupant use of interior shading devices is one of the most influential factors in the admission of daylight into the buildings. Based on a number of observations, occupants don't adjust shading devices frequently, and once lowered, the blinds are left in place for days or even weeks leading to reduced energy savings from daylight. Previous shade control behavior studies focus on environmental conditions such as transmitted vertical irradiance to predict the deployment of the shades; while there have been very few studies focusing on the factors that affect the raising of the interior shading devices by the occupants. This paper examines the effect of an interior lightshelf system on occupants' use of blinds and electric lighting. The results suggest that in identical environmental conditions, occupants whose workstations were located within the lightshelf zone demonstrated a lower window occlusion than those who were located in the area with conventional windows. Additionally, occupants in the lightshelf zone used less electric lighting than those in regular window design area.

Conventional fixed shading devices in comparison to an electrochromic glazing system in hot, dry climate

Electrochromic glazing or exterior shading devices offer shading of the intense direct sun, reduce glare, and improve the daylight luminance within buildings. Additionally, they are important factors affecting energy performance of buildings as they impact the heating and cooling consumption. This analysis investigated the performance and the effectiveness of electrochromic glazing to prevent unwanted solar heat gains from entering a conditioned space. Then, these performances are compared to those offered by conventional fixed exterior shading devices in identical conditions. The aim of this analysis is to provide architects and designers with general guidance and appropriate design strategies for different window treatments and shading techniques during early design stages in hot, dry climate. A typical office building is modeled using DesignBuilder software. Building envelope characteristics, internal loads, and operating schedules including schedules for equipment, occupancy, interior lighting, heating, ventilating, air conditioning, and weather data are all unchanged throughout the simulation process. The windows shading condition and the glazing type are the only varying parameters. The output data show that electrochromic glazing provides the best performance in reducing solar heat gains compared to other tested shading conditions.

Review: Metabolism: The City of the Future

Metabolism: The City of the Future . Mori Art Museum, Tokyo. 17 September 2011–15 January 2012. Today we often regard Japan’s Metabolists as young dreamers proffering technologically advanced, audaciously overscaled schemes. A show at the Mori Art Museum in Tokyo—the first retrospective dedicated to the group—underscored instead Metabolism’s ideological origins and, more importantly, unearthed a treasure trove of artifacts. The exhibition opened with a single image: a 1953 photograph of Kenzo Tange’s celebrated central structure at Hiroshima’s Peace Park. The Metabolists’ debut was still seven years away, via a booklet distributed at the 1960 World Design Congress in Tokyo that featured four architects—Masato Otaka, Kiyonori Kikutake, Fumihiko Maki, and Kisho Kurokawa—and others from related disciplines: author and editor Noboru Kawazoe, industrial designer Genji Ekuan, and graphic designer Kyoshi Awazu.1 Adjacent Japanese and English wall text used to isolate this image argued that Tange, though not a member of the movement, was its progenitor; the point was then followed by additional photographs of Peace Park interspersed with rarely seen construction and presentation documents from the Tange office, many now held by Harvard’s Frances Loeb Library. A public housing complex designed by Masato Otaka, built on an adjacent plot, was served up subsequently on the same wall. The Mori exhibition thus presented its first Metabolist with a subtlety that was untypical of the movement itself, via a grouping of residential towers overshadowed by Tange’s masterwork—an unappreciated complex not completed until the 1970s, designed by the only Metabolist architect who was more interested in Japan’s proletariat and never established an international reputation. The opposite wall of this opening gallery offered a historical preamble to the exhibition: on a panel some 45 feet long, a timeline tracked Japan’s population and economic growth from 1905 through 1960. Set against the data were computer animations, reproductions of photographs, and recently built models related to a period long ignored in polite circles: …

Experimental Analysis of Flat Plate Solar Air Collector Efficiency

In the present study, a flat plate solar air collector is used for research purposes. The absorber of solar collector made by steel plate with an area of 2×1m 2 and thickness of 0.5mm in the form of window shade has been developed for increasing the air contact area. The surface of absorbent plate was covered by black paint. To insulate the collector, the glass wool with the thickness of 5cm was used. The experiments on the efficiency were conducted for a week during which the atmospheric conditions were almost uniform and data was collected from the collector. The results of the collector efficiency in the natural and forced convection were evaluated and their graphs were plotted. The results showed that the collector efficiency in forced convection was lower, but the low temperature difference between inlet and outlet of the collector decreased its heat loss. In addition, the average air speed in forced convection was about 21% higher than the natural convection.

External perforated window Solar Screens: The effect of screen depth and perforation ratio on energy performance in extreme desert environments

In hot arid desert environments, the solar radiation passing through windows increases the cooling loads and the energy consumption of buildings. Shading of windows can reduce these loads. Unlike the woven solar screens, wooden solar screens have a thickness that provides selective shading properties. Perforated wooden solar screens were traditionally used for windows shading. Developing modern types of these shading systems can lead to significant energy savings.The paper addresses the influence of changing the perforation percentage and depth of these screens on the annual energy loads, hence defining the optimum depth/perforation configurations for various window orientations. Series of experiments were performed using the EnergyPlus simulation software for a typical residential building in the Kharga Oasis, located in the Egyptian desert. A range of perforation percentages and depths were tested.Conclusions prove that external fixed deep perforated solar screens could effectively achieve energy savings up to 30% of the total energy consumption in the West and South orientations. Optimum range of depths and perforation percentages were recommended. These are: 80–90% perforation rate and 1:1 depth/opening width ratio. These lighter and deeper solar screen configurations were found to be more efficient in energy consumption in comparison with the traditional ones.

Building façade design for daylighting quality in typical government office building

Daylighting is one of the potential passive strategies to improve energy performance and users' visual comfort in existing offices without expensive installation and operational cost. For the first time, empirical study of daylighting performance was conducted for an existing typical government office building designed by Public Work Department (PWD) in Malaysia. Daylight field measurement of external illuminance and internal work plane illuminance was carried out. The findings demonstrated that internal daylight level in the building was insufficient despite the abundance of external daylight availability in the tropics which can achieve as high as 130 klx. Validation of simulation using Radiance-based software against the measurement under actual tropical sky indicated significant Pearson correlation of 0.709. Then, modification of window glazing and shading devices was experimented with simulation. The findings evidenced that light shelf increased daylight distribution uniformity, but failed to reduce glare on vertical plane when direct sunlight patches occurred. Integration of light shelf with partial blinds tilted at 45° showed improved performances of mean Guth Visual Comfort Probability (VCP) and CIE Glare Index. This paper concludes that simple modification of window glazing and shading device is able to provide significant improvement in tropical daylighting quantity and quality for visual comfort.

The Complex Fenestration Construction: a practical approach for modelling windows with shading devices in ESP-r

The use of operable shading devices impacts building loads significantly. The need exists for an explicit treatment of window shading devices in the design of energy-efficient buildings through simulation. A general framework for modelling complex fenestration systems, the Complex Fenestration Construction (CFC), has recently been implemented in ESP-r. The underlying models have been developed with emphasis on computational efficiency and straightforward input requirements. The capabilities are summarized, and an overview of the solar-optical and thermal models is given. Simulations were carried out comparing the CFC in ESP-r to slat-type blind models in EnergyPlus. The results show good agreement between the two simulation programs. Work is ongoing to expand the types of shade layers available with the CFC.

A study on the spread of fire caused by the stack effects of patio—A computer modeling and a reconstruction of a fire scenario

This study reported an actual building fire incidence for a ten-story building that occurred in Taiwan in 2008. Due to the stack effects the fire occurred on the third floor spread through the patio in a short time to the upper floors and caused three deaths in a tenth floor apartment. This study also attempted to reconstruct the actual fire scenario using computer simulation. The spread of the fire to the combustibles due to hot smoke was accounted for in the simulation. Variation of the fire scenario and the factors causing the fire spread were studied. It was found that an initial fire size below 1.0 MW would not generate sufficient hot smoke to cause fire spread despite the stack effects. However, any obstructions in the patio such as window shading has been found to cause heat accumulation that would aggravate the fire spread problem. The presence of a canopy at the top of the patio can cause higher concentration of smoke for the upper floors. The simulation results are found to be in good agreement with the actual incidence. Moreover the simulation results also show that when the fire spread through the patio the initial fire size of 1.0 MW at the fire site can grow to a building fire of 300 MW.

Optimization method for building envelope design to minimize carbon emissions of building operational energy consumption using orthogonal experimental design (OED)

Climate change has drawn the attention of many researchers and practitioners to focus on the methods to address the challenges in achieving low-carbon buildings and cities and in future developments. Nevertheless, few studies have explored the application of orthogonal experimental design (OED) method to optimize building design for the lowest carbon emissions of building operational energy consumption. This paper aims at developing a new optimization method to building envelope design for the lowest carbon emissions of building operational energy consumption using OED. Firstly, according to the basic principles of the building heat transfer, the method of building’s energy consumption calculation is analyzed, which includes the simplified algorithm based on steady-state heat transfer theory and the dynamic simulation based on the unsteady heat transfer theory. The classification of the building energy consumption influencing factors are then investigated and discussed. Furthermore, based on the basic concept and principle of OED, a case study from the perspective of OED has been conducted, which involves a public building in Nantong, Jiangsu province. Six influence factors of building envelope to building operational energy consumption are selected as follows: exterior wall type, window frame type, glass type, roof type, floor type, and shading type. Selection of optimal case is then determined by the index that is based on the year-round accumulative total load. In the end, Tianzheng Building Energy Consumption Software is used to calculate the optimal case operational energy consumption. The research would provide a new optimization method for building envelope design to the lowest carbon emissions of building operational energy consumption.

Comparison of building load performance between first principle based and implementable shading control algorithms

This paper presents the findings on the impact of two window shading control strategies on office building thermal and lighting loads over a year’s period through energy simulation in four different climatic contexts in the United States. While it is well known that window shades affect heat gain and loss through windows and thus building energy loads, there is limited information on the actual magnitude and specific behavior of their effects on the building thermal and lighting loads. The objective of the described study is to generalize the magnitude of the impact from window shading control strategies on building thermal and lighting loads over a year by modeling a representative office building construction in indicative geographical locations as well as internal window shades representative of those that are commonly used. Two control algorithms are developed and evaluated which are the ideal algorithm and implementable. The basic principle of both algorithms is to maximize heat gain and minimize heat loss when the building is in heating condition, and performs the opposite when the building is in cooling condition, subject to glare control. Some of the information that is used in the ideal algorithm is not available for a “real world” controller. Therefore, an implementable shading control algorithm is also described, which will take sensor measurable conditions as input. EnergyPlus is used to conduct the thermal and lighting loads computation. The control algorithm is implemented through the BCVTB (Building Control Virtual Test Bed). BCVTB is a software environment that allows expert users to couple different simulation programs for distributed simulation.

Assessment of the Portuguese building thermal code: Newly revised requirements for cooling energy needs used to prevent the overheating of buildings in the summer

In this paper, cooling energy needs are calculated by the steady-state methodology of the Portuguese building thermal code. After the first period of building code implementation, re-evaluation according to EN ISO 13790 is recommended in order to compare results with the dynamic simulation results. From these analyses, a newly revised methodology arises including a few corrections in procedure. This iterative result is sufficiently accurate to calculate the building’s cooling energy needs. Secondly, results show that the required conditions are insufficient to prevent overheating. The use of the gain utilization factor as an overheating risk index is suggested, according to an adaptive comfort protocol, and is integrated in the method used to calculate the maximum value for cooling energy needs. This proposed streamlined method depends on reference values: window-to-floor area ratio, window shading g-value, integrated solar radiation and gain utilization factor, which leads to threshold values significantly below the ones currently used. These revised requirements are more restrictive and, therefore, will act to improve a building’s thermal performance during summer. As a rule of thumb applied for Portuguese climates, the reference gain utilization factor should assume a minimum value of 0.8 for a latitude angle range of 40–41°N, 0.6 for 38–39°N and 0.5 for 37°N.

Optimum design of a house and its HVAC systems using simulation-based optimisation

This paper deals with a multi-objective optimisation problem where the objective is to minimise CO 2 -eq emissions and investment cost of a multi-zone single-family house and its heating/cooling systems. Eight design variables are subjected to study: level of building tightness, insulation thickness of the external wall, floor and roof, type of window glazing, window shading, heat recovery and heating/cooling systems. Simulation-based optimisation is implemented to minimise the objective functions by finding optimum values of the design variables. This is done by combining the dynamic building performance simulation program IDA-ICE 3.0 with a modified genetic algorithm. The optimisation results give the optimal solutions for the problem in the form of a Pareto front, showing the trade-off between the two objectives. The obtained solutions are much better than the initial designs of the house in terms of lower CO 2 -eq emissions and investment cost. It is noted from the obtained results that the significance of the heating system is higher than the other design variables so that the optimal solutions can be classified according to the type of the heating system. It is also noted that there is a need to include a thermal comfort criterion as a problem constraint to limit overheating hours during summer. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.

Advanced External Shading Device to Maximize Visual and View Performance

Controlling or avoiding direct sun beam shining into the interior is a key criterion for consideration in most architectural daylighting designs. This treatment is mainly intended to attenuate the adverse glare and contrast associated with direct sunlight and to lessen the negative contribution of direct sunlight on the cooling load. Window shades are commonly used in Korea to reduce heat gains in the form of direct beam radiation, particularly in summer. Very often they consist of non-movable structures, such as overhangs, vertical fins or composition of both, forming eggcrate-type systems, and ideally should be designed by incorporating these methods. One of the simplest sunlighting controls is Venetian blind. It plays a role in excluding direct sunlight but reflecting light to rear interior, while still allowing a view to exterior. The blinds also go far toward improving uniformity in illuminance. External shading devices are much more effective than internal shading devices. However, it is not popular because of cost, maintenance, and esthetic reasons. We developed an experimental configuration of external shading device, providing better performance of shading and view. A series of simulations and measurements have verified the differentiated advantages in illumination and building energy consumption by using this system.

Sensitivity analysis of building energy use in different climates

Key design parameters (in terms of their influences on building energy consumption) through sensitivity analysis for fully air-conditioned office buildings in five cities (Harbin, Beijing, Shanghai, Kunming and Hong Kong) representing the five major climate zones (severe cold, cold, hot summer and cold winter, mild, and hot summer and warm winter) across China have been identified. These include: i) building envelope - window shading coefficient, window U-value and window-to-wall ratio; ii) internal load – equipment, lighting and occupancy; iii) HVAC system - outdoor fresh air, summer and winter thermostat set points, fan efficiency and fan static pressure; and iv) HVAC plant – chiller COP and boiler efficiency. The influence coefficient (IC, a ratio of the percentage change in computed output (building energy use) to the percentage change in input design parameter was used to indicate likely energy savings. For instance, Hong Kong has a lighting load IC of 0.359, suggesting that a 20% reduction (e.g. from 18 to 14.4 W/m 2 ) in lighting load could result in more than 7% reduction in the total building energy use. Furthermore, Hong Kong also has a summer thermostat set point IC of -1.131, suggesting that a 5% increase in the indoor temperature during the summer (e.g. from 26 to 27.3 o C) could result in about 6% energy savings. Given the growing awareness of adaptive thermal comfort, this could be a no-cost energy-efficient measure with great energy saving potential.