External Shading Research Articles

A Study on the Impact of Different Cooling Methods on the Indoor Environment of Greenhouses Used for Lentinula Edodes during Summer

The shitake mushroom (lentinula edodes) industry in the Gobi Desert region of southern Xinjiang has experienced rapid development and has reached a certain scale. To clarify the laws governing different cooling methods in greenhouses and identify suitable cooling methods for mushroom production in the Gobi Desert region, this study focused on monitoring the environmental changes in greenhouses using three different cooling methods: natural ventilation cooling, water-sprinkling roof cooling, and a fan and pad cooling system. The results showed that when combined with external shading (shade netting), natural ventilation cooling, fan and pad cooling, and water-sprinkling roof cooling, respectively, reduced the air temperature by 8.6 °C, 14.0 °C, and 15.2 °C. They also increased the relative humidity by 15.3%, 43.3%, and 51.2%, resulting in cooling efficiencies of 28.5%, 56.3%, and 68.1%, respectively. The water-sprinkling roof cooling system demonstrated the best cooling effect and temperature uniformity and had higher economic benefits. Therefore, the use of the external sprinkler cooling method in double-skeleton greenhouses is suitable for summer lentinula edodes production in the Gobi Desert region of southern Xinjiang.

Evaluation of thermal performance and energy efficiency of a Trombe wall improved with dual phase change materials

Trombe Wall (TW) as effective passive solar design technology can improve the building's energy efficiency and thermal comfort. TW may not be very effective alone. Adding Phase Change Materials (PCMs) to TW improves the efficiency to compensate for this shortcoming. In this paper, for better efficiency, a new double-layer Phase Change Material Trombe Wall (PCMTW) containing two layers of different PCMs with different phase-changing points on the exterior walls of the building was proposed. This paper aimed to compare the thermal performance of different models of double-layer PCMTW in different air gap thicknesses and different PCM combinations with a base state. The results show that classical TW with an air gap thickness of 20 cm reduces energy consumption by 34% in winter. The best air gap thickness for the PCMTW was 20 cm too, and the energy consumption was reduced by 39% in this air gap thickness. Also, there was little difference in the energy consumption of the three models in the summer, and the overheating phenomenon was solved by considering external shading. for solving this effect in summer, the best length of external shading was 50 cm.

Energy simulation on how to go green buildings in an earth's dry climate

Green buildings, i.e. low-energy and environmentally-friendly buildings, are highly demanded for optimizing the energy consumption and reducing the Green House Gas (GHG) Emissions. In this study, energy consumption of a residential building is analyzed in the hot and dry climate of Kashan, Iran. This is done based on the criteria of green buildings, using the Design Builder software. Several approaches are presented and discussed for the analysis, including the installing a thermal insulation layer, using external shadings and interior curtains, regulating the optimal comfort temperature, using an economizer, regulating the optimal domestic heat water (DHW) temperature, and installing photovoltaic panels. We investigate heating and cooling energies, as well as the total amount of energy saving in different conditions of the building. The results demonstrate that using the presented strategies leads to 67% and 39.3% reductions in electricity and gas consumption, respectively. Also, the carbon dioxide emissions are decreased 50.5% as a result of implementing the proposed methods.

Correlations for forced convective heat transfer coefficients at the windward building façade with vertical louvers

Vertical louvers are a widely used external shading system to control natural lighting and solar heat gain for buildings. However, when installed on a building façade, they can disrupt the flow field around the façade and affect the external convective heat transfer process of building's exterior surfaces. To this end, this paper conducted CFD simulations to clarify the forced convective heat transfer patterns in a vertical louver-facade system based on the k-ω SST model with a detailed verification. The extended Newton's cooling equation is used to describe the heat exchange process between louvers, building façade, and air, which generates four heat transfer coefficients: hwa, hwb, hba, and hbw. Then the impacts of dimensionless temperature difference (θ), louver angle (φ), louver slat width (B), and installation distance (W) on the heat transfer coefficients are investigated. The results show that θ does not affect the average heat transfer coefficients. hwa reaches a minimum value and hba reaches a maximum value when φ = 75o. In addition, hwa increases by 55.3% and hba decreases by 21.9% as B increases from 0.3 m to 1 m. When W increases from 0.25 m to 1 m, hwa decreases by 5.6% and hba increases by 39.6%. The variation in the heat transfer coefficients (hwb and hbw) between the louvers and building façade is also explained. Finally, new correlations of paired heat transfer coefficients are established as a function of φ, B, W, and wind velocity (U10). The accuracy of these correlations is evaluated by comparing calculated values with simulated results.

Identifying external louver angle for residence opening to optimize the indoor environment for the composite climate of Delhi NCR

The essential part of any shading device is to intercept the solar radiation in such a manner that it allows enough daylight inside the building, while at the same time the indoor thermal comfort is upheld for all the seasons. Earlier studies proved that in comparison with internal shading devices, the external ones minimize the internal heat gain in an effective manner by blocking the radiation, before it reaches the fenestration glazing. However, fixed external shades are incapable of balancing the varying requirements of light and heat for different climatic conditions. Mainly, summer and winter in the composite climate demands adaptive shading solutions as per the changing season. The current study is an attempt to evolve appropriate external adaptive louver shades and recommend louver angles for different months, for a single space of a typical apartment building in Delhi NCR region. The recommended angles allow the occupants to make informed decisions by manually adjusting the louvers to improve the indoor environment. This study utilized ladybug and honeybee plugins for the purpose of simulation. The results show that the monthly adjustments of external adaptive shades enhance the indoor environment and save energy. The study developed, analysed and compared two different types of external adaptive louver shading systems such as EALS (External Adaptive Louver Screen) and EALA (External Adaptive Louver Awning) for better indoor environment and energy saving for west orientation.

External shading and its effect on the energy efficiency of Tehran's office buildings

AbstractModern office building designers tend to propose highly glazed façades that provide occupants with a view and daylight; however, the use of such façades has consequences, like glare and high energy consumption, especially in warm climates. Shadings affect energy usage for cooling, heating, and artificial lighting, defined as the objectives and output in the optimizer algorithm. The input variables are shading type, WWR, the depth of the shading, the distance between the shading and the window, the distance between fins, the number of fins in shading, and the distance from the top of the window. This research aims to comprehensively study external shadings and window‐to‐wall ratios to reduce the high energy consumption in modern office buildings in Tehran and cities in locations with a similar climate. The results can benefit all scientists researching building science, architects, instructors, and those wanting to buy a low‐energy consumption office. Energy consumption was calculated in Ladybug–Honeybee; the best objectives were obtained for each shading with the optimization process by the Octopus plugin in Grasshopper. Results were analyzed and rated compared with a window without shading. The best scenario was obtained for Egg‐crate with a 14.86% reduction in cooling energy and a 20.04% increase in useful daylight illuminance.

Windows of Opportunities: Orientation, Sizing and PV-Shading of the Glazed Area to Reduce Cooling Energy Demand in Sub-Sahara Africa

In hot climates, such as sub-Sahara Africa, window sizing and orientation pose challenges as they add, through solar insolation, to the building cooling energy demand and thus the cause of indoor overheating risk. This risk can be reduced through passive building-design-integrated measures, e.g., optimizing the window size, orientation and solar shading strategies. Through an IDA-ICE building performance simulation tool, the current study explores the impact of window size, optimization and building-integrated PV panels as shading strategies on cooling energy demands in three cities (Niamey, Nairobi and Harare) in sub-Sahara Africa. Results show that thermal comfort and cooling energy demand are sensitive to a window-to-wall ratio (WWR) > 70%, while the need for artificial lighting is negligible for a WWR > 50%, particularly in the north for cities in the Southern hemisphere and the south in the Northern hemisphere. A WWR > 70% in the east and west should be avoided unless shading devices are incorporated. Internal blinds perform better in improving occupant thermal comfort but increase artificial lighting while integrating PV panels, as external shading overhangs reduce cooling energy but also produce energy that can be utilized for building services, such as air conditioning. In this study, the results and implications of the optimization of window size, orientation and building-integrated shading and operation are discussed.

Passive Intelligent Kinetic External Dynamic Shade Design for Improving Indoor Comfort and Minimizing Energy Consumption

In humid subtropical climates with a green environment, windows are the most dominant envelope elements affecting indoor visual and thermal comfort and visual connection to the outdoors. This research aims to optimize a dynamic external shading system for north-facing windows in Sydney, Australia, which acts automatically in eight predefined scenarios in response to indoor comfort conditions. The method of investigation was simulating a multi-objective optimization approach using Non-dominated Sorting Particle Swarm Optimization (NSPSO) to assess visual and thermal comfort along with energy usage and view of the outside. A combination of human and sensor assessments were applied to validate the simulations. A set of sensors and High Quality (HQ) cameras fed the system input to operate the shade. Simulations and field measurements demonstrated that optimized shading scenarios brought average yearly reductions of 71.43%, 72.52%, and 1.78% in Annual Solar Exposure, Spatial Daylight Glare, and LEED Quality View, respectively, without sacrificing Daylight Autonomy. Moreover, yearly improvements of 71.77% in cooling demand were achieved. The downside of the shading system was an increase of 0.80% in heating load and 23.76% in lighting electricity, which could be a trade-off for improved comfort and energy savings. This study investigated the effect of dynamic external shade on visual and thermal comfort together with energy usage and view, which has not been investigated for southern-hemisphere dwellings. A camera-sensor-fed mechanism operated the external shade automatically, providing indoor comfort without manual operation.

放射パネル冷房と窓開け換気との併用を実践している住宅の実測調査

This paper describes results of a field measurement on air and thermal environment in a residential building where both radiant cooling and ventilation are realized. Combination between radiant cooling and ventilation can keep indoor CO2 concentration less than 1000 ppm and room air temperature s and MRTs 28°C or less. Radiant cooling uses less power than air conditioners with similar COP to the heat pump of panel cooling and is not remarkably affected by incoming outside air. Even if ventilation is done, external shading can realize the same SET＊ with higher panel temperatures than the case of non-shading.

Daylight optimization in a hypothetical classroom using single-objective optimization methods: Case study in Lhokseumawe, Indonesia

This study evaluates and optimizes daylighting performance in a hypothetical classroom located in Lhokseumawe, Indonesia. The classroom daylighting performance is represented by the metrics aUDI250-750lx, sDA300/50%, and ASE1000,250. Under the baseline conditions, poor daylighting performance was revealed as indicated by a low aUDI250-750lx value and a high ASE1000,250h value. To obtain good daylighting performance, this study utilized a computational simulation method using Rhinoceros, Grasshopper, and Honeybee Plus platforms. Optimization is conducted using Opossum with the RBFOpt algorithm. The optimization result suggests the building envelope design parameters and external shading device design which results in a better natural lighting performance as indicated by the increase of aUDI250-750lx value at about 45%, the sDA300/50% value remaining at around 94%, and the ASE1000,250h value has decreased by 14% compared to the baseline condition of the classroom.

IMPACT OF WINDOW SHADING ON THE THERMAL PERFORMANCE OF RESIDENTIAL BUILDINGS OF DIFFERENT FORMS IN JORDAN

Introduction: Window shading is considered one of the most effective passive design approaches that improves indoor thermal performance, minimizing the usage of HVAC and reducing energy consumption. Purpose of the study: We aimed to investigate the impact of external window shading on thermal performance of three existing residential buildings having different forms (rectangular, L-shaped, and U-shaped) in hot-dry climate in Amman, Jordan. Methods: Three types of shading, namely: vertical, horizontal, and combined, of different lengths (0.75 m, 1.00 m, and 1.25 m) were introduced to the existing buildings. The effect of those types of shading was studied using the OpenStudio SketchUp 2020 plugin and EnergyPlus simulation program. Results: It was established that vertical shading slightly improves the indoor air temperature in all building forms, while horizontal shading and combined shading improve the thermal performance of buildings to a more significant extent. Combined shading of 1.25 m in length shows the optimum behavior in all buildings since it reduces the indoor air temperature in the range of 2.6–3.3°C. Besides, it improves thermal sensation, which seem to be closer to the comfort zone, by reducing the predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) values as compared with the baseline situation without shading. In addition, the rectangular building demonstrated the best response for shading by showing the largest reduction in the indoor air temperature.

An Appraisal of Double Skin Facade in Building Design: Architectural Intervention and Sustainability

One of the key issues in twentieth-century architecture is the energy problem and daily rise in environmental pollution brought on by the creation of greenhouse gases, particularly in the construction industry. The purpose of the research that follows is to investigate how well buildings heat up while also updating double-skinned facades to ensure thermal comfort for the residents while using the least amount of energy possible. The thoughtful design of a building's exterior is one of the most crucial ways to conserve energy in that structure. The finest choice for controlling the interplay between the interior and exterior spaces is a ‘double-skin facade’. Double-skin facades have been used more frequently recently to increase transparency in both building renovations and new construction. Although glare issues may worsen, double-skin facades improve lighting levels and the outside view. When comparing a typical glass facade to one with an additional layer of glazing, it is possible to reduce heat loss and outside noise. A very critical concern appears to be the protection of external solar shading devices against wind and deterioration. This paper reviews and discusses the earlier research on double-skin building facade systems. The evaluation of a double-skin facade system for long-term building envelope or infrastructure development is the main theme of the paper.

Retrofitting of a High-Rise Residential Building for Energy Efficiency with OTTV as an Assessment Tool

Buildings account for nearly 50% of the total energy consumption. The use of air-conditioning is one of the major influencers to the high energy consumption in buildings. To tackle this high energy consumption, buildings are required to be more energy efficient. This study aimed to investigate the retrofitting of existing residential building for energy efficiency by using the Overall Thermal Transfer Value (OTTV) as an assessment tool. Various retrofitting measures were involved, including varying the colour of the opaque wall with different solar absorptivity, the U-value and shading coefficient of the Glazing system, and the type and projection of the external shading. The results showed that applying the retrofitting measures individually (i.e., using light colour with low solar absorptivity, replacing the glazing system to have lower shading coefficient and U-value, and the installation of external shading systems with low shading coefficient) can decrease the OTTV by 26% to 33.4%. However, combining these measures managed to decrease the OTTV by up to 75.6% (i.e., the OTTV decreased from 82.87 W/m² to 20.19 W/m²). This can improve the building energy efficiency as it contributes to less cooling load for the air-conditioned buildings, while it provides a better indoor environment in non-air-conditioned buildings.

Study of the tools used for early-stage carbon footprint in building design

The purpose of this study is to construct a digital tool and design process for building a carbon footprint calculation to change the current status of Taiwan's carbon footprint calculation in post-use assessment, and to incorporate both carbon emissions and energy consumption in the environmental impact assessment into the initial considerations of the architectural design. Through the connection of carbon emission calculation tools and optimization tools, the advantages and disadvantages of multiple schemes in relation to carbon emissions and energy consumption can be compared simultaneously, thereby assisting designers to achieve faster results when making design decisions. In addition to the building's area, orientation, and height, various schemes could also further facilitate architectural design plans with lower carbon emissions by adjusting factors such as the external shading depth and the window-to-wall ratio by calculating the building dimensions to pursue the maximum percentage of the visual field (maximum window area), thereby reducing carbon emissions. This study is expected to meet the needs of users by simplifying the calculation tools and operation interface required for carbon emission calculations, visualizing the calculation results, and enabling a comparison of multiple design schemes. In addition, it provides recommended projects that can be reviewed in the early decision-making stage of the architectural design process, and provides designers and planners with approximate building carbon emission calculations for projects. Furthermore, to facilitate a calculation process with the best view, the scheme simulation is optimized under the existing design conditions, and the optimal solution (Pareto optimal solution) is obtained following calculation classification and analysis. The simulated data can be listed for design reference, whereby users can make design decisions based on the design conditions.

Domestic overheating risks and mitigation strategies: The state-of-the-art and directions for future research

Anthropogenic climate change will likely put dwellings at risk of overheating and potentially increase cooling demand in the decades ahead, leading to higher greenhouse gas (GHG) emissions due to the energy consumed for mechanical cooling. Contemporary constructions with highly insulated fabric have been found to suffer from periodic overheating in today’s climate, the occurrence of which is projected to increase in frequency as the temperature rises. This critical review investigates the factors affecting overheating risks in dwellings and passive cooling strategies to mitigate overheating impacts on occupant thermal comfort and wellbeing. The cooling efficiency of passive strategies is affected by the design, construction and operation of buildings, as well as climate and occupancy. A framework has been developed to illustrate the effect of overheating factors on the cooling efficacy of passive strategies. Findings suggest that a combination of passive strategies is required to minimise overheating risks by the 2080s. External solar shading is the most effective method for retrofitting insulated dwellings. On the other hand, cool paint is ideal for uninsulated dwellings. In addition, thermal mass and natural ventilation require occupant interaction for optimal air circulation and cooling performance.

Research and Exploration of Green Building Based on the Basic Theory of Urban Development

Firstly, the influence of building design factors on building carbon emissions was analysed, and the influence of building form factor, building orientation and building envelope on building carbon emissions was simulated and studied, which shows that the south-facing direction has the lowest building carbon emissions, the external window shading factor is negatively related to building carbon emissions, and all other factors are positively related to building carbon emissions. The existing low carbon evaluation systems were then analysed, most of which suffer from a lack of carbon emission calculation methods and a lack of comprehensive scoring methods. This paper establishes an evaluation index system based on the principles of evaluation system construction, determines the benchmarks for index evaluation based on energy saving standards and research data, delineates the range of evaluation index parameters and the percentage of scores, and establishes an evaluation index system. The weights of the evaluation indicators were calculated using hierarchical analysis and combined with expert questionnaires, and a comprehensive scoring method was established based on the weights to build a building carbon emission evaluation system.

A simulation-based study to evaluate the cooling potential of nocturnal radiative cooling systems for residential buildings in Egypt

During the first years of the last decade, Egypt used to face recurrent electricity cut-offs in summer. In the past few years, the electricity tariff dramatically increased. Radiative cooling to the clear night sky is a renewable energy source that represents a relative solution. The dry desert climate promotes nocturnal radiative cooling applications. This study investigates the potential of nocturnal radiative cooling systems (RCSs) to reduce the energy consumption of the residential building sector in Egypt. The system technology proposed in this work is based on uncovered solar thermal collectors integrated into the building hydronic system. By implementing different control strategies, the same system could be used for both cooling and heating applications. The goal of this paper is to analyze the performance of RCSs in residential buildings in Egypt. The dynamic simulation program TRNSYS was used to simulate the thermal behavior of the system. The relevant issues of Egypt as a case-study are firstly overviewed. Then the paper introduces the work done to develop a building model that represents a typical residential apartment in Egypt. Typical occupancy profiles were developed to define the internal thermal gains. The adopted control strategy to optimize the system operation is presented as well. To fully understand and hence evaluate the operation of the proposed RCS, four simulation cases were considered: 1. a reference case (fully passive), 2. the stand-alone operation of the RCS, 3. ideal heating & cooling operation (fully-active), and 4. the hybrid-operation (when the active cooling system is supported by the proposed RCS). The analysis considered the main three distinct climates in Egypt, represented by the cities of Alexandria, Cairo and Asyut. The hotter and drier weather conditions resulted in a higher cooling potential and larger temperature differences. The simulated cooling power in Asyut was 28.4 W/m² for a 70 m² absorber field. For a smaller field area of 10 m², the cooling power reached 109 W/m² but with humble temperature differences. To meet the rigorous thermal comfort conditions, the proposed sensible RCS cannot fully replace conventional air-conditioning units, especially in humid areas like Alexandria. When working in a hybrid system, a 10% reduction in the active cooling energy demand could be achieved in Asyut to keep the cooling set-point at 24 °C. This percentage reduction was nearly doubled when the thermal comfort set-point was increased by two degrees (26 °C). In a sensitivity analysis, external shading devices as a passive measure as well as the implementation of the Egyptian code for buildings (ECP306/1–2005) were also investigated. The analysis of this study raised other relevant aspects to discuss, e.g. system-sizing, environmental effects, limitations and recommendations.

The acoustic and daylighting effects of external façade sun shading systems

External sun shading devices are increasingly used in sustainable buildings to reduce the greenhouse effect in the summer and the glare effect due to direct solar irradiation through transparent surfaces. The acoustic effects of these devices have been investigated in recent studies that suggest the possibility of optimising these elements to improve acoustic comfort in indoor environments, even with open windows. Nevertheless, there are few studies that analyse the combined effect of these devices on acoustic attenuation and improved daylighting. In this paper, the results of acoustics and daylighting simulations are reported, considering different dimensions, distances of the louvres and orientations of the façade. The main results of previous works concerning the effect of lining the bottom side of each louvre with sound-absorbing material are also briefly summarised. The acoustic effects of different configurations of the louvres are evaluated in terms of Insertion Loss in the façade plane. For the lighting simulations (daylight factor, daylighting uniformity and daylight glare probability), the variation of the shielding effect is studied considering the spacing between the louvres and the orientation of the façade for different times and seasons for latitude in the South of Europe.

Green Building Concepts and Technologies in Ethiopia: The Case of Wegagen Bank Headquarters Building

The building sector is a key contributor to climate change, accounting for 40% of global energy consumption and 39% of CO2 emissions. Presently, green buildings have been viewed as crucial strategies to reduce the negative effects of the construction sector. Yet green building research is often carried out in developed countries, while relatively little is known in sub-Saharan African countries. Therefore, this study attempts to investigate the extent of adoption of green building concepts and technologies in Ethiopian buildings, with particular reference to the Wegagen Bank Headquarters building. The study employed an interview, which was underpinned by observation. The quantitative data were analyzed through descriptive statistics while the qualitative data were analyzed through content and context analysis. Results revealed that while the building provides convenient access to transportation; it lacks designated open spaces. Based on the findings, the widely used technologies were energy-saving lighting, highly efficient plumbing fixtures, and external solar shading system. Lack of awareness, lack of policy, insufficient professional skills, the perception that green buildings are expensive, and lack of green building materials hindered the adoption of the concepts. Therefore, the study suggests developing green building policy and rating systems, professional capacity building, and awareness creation as important measures.

Adapting façade performances to climate change in northern Europe: Analysis of future scenarios for an office building in Stockholm

Future climate change will affect many human activities and sectors. Among those, the built environment will face several challenges about the varying climate conditions, including increased demand for summer cooling and related heat stress indoor conditions. In this framework, the paper presents the results of a recent study that investigated the global warming impacts on energy demand and indoor climate comfort for an office building in Stockholm over the next 50-60 years. The future climate conditions were investigated in 2070 and 2080 with different climate morphing approaches. Three different passive cooling solutions to decrease the cooling demand (such as external roller shade, electrochromic glazing, and internally ventilated shading) have been preliminarily assessed about thermal and optical properties, then integrated into the building energy simulation software IDA-ICE to evaluate the building energy performances regarding different Swedish climates, and finally economically estimated with a simplified LCC analysis. The results indicated that an increment of the cooling demand from 3 up to 24 kWh/m2 and a reduction of the heating usage of 20-50 % will be experienced in 50-60 years. The different weather data morphing approaches displayed the inherent uncertainties when future evaluations are performed, although similar weather patterns were found. The improvement of the solar and optical properties indicated a lower cooling and ventilation usage with reductions of about 10-16 %. The electrochromic technology reported the lowest cooling demand (decrease up to 24 %), while the internally ventilated shading option outperformed the others with anannual energy consumption 4-9 % lower and the lowest LCC.