Window-wall Ratios Research Articles

Restorative benefits of classroom windows: a study on the effect of window:wall ratio on task load and learning performance based on VR technology

Abstract As a connection to the outdoor environment, windows can relieve the stress, emotional, and cognitive fatigue that building users face from long hours of study. It provides restorative function for building users between study and work, thus reducing task load and improving learning performance. To investigate the effects of different window:wall ratios (WWRs) on task load and learning performance, virtual reality (VR) technology was used to build virtual classrooms with WWRs of 25%, 40%, 55%, 70%, and 85%. The task performances, physiological data, and subjective evaluations of 34 college studies were analyzed. It was found that the highest subjective psychological loads were in classrooms with a 25% WWR and were lowest when the WWR was 55%. Participants performed best in classrooms with a WWR of 55%. Further multiobjective optimization with particle swarm optimization found that 58.41–62.24% WWR not only contributed to the users’ physical and mental happiness but also improved their learning efficiency. In addition, the participant’s HRV-LF/HF and EEG β wave values were significantly correlated with their performance on the task test. These findings provide a reference for the spatial design of school classrooms and a foundation for further research into the relationship between HRV and EEG physiological indicators and learning efficiency.

Comparing overheating risk and mitigation strategies for two Canadian schools by using building simulation calibrated with measured data

This paper compares the indoor overheating risk of two schools by considering the effect of selected building parameters, under extreme current and future climates, and proposes mitigation strategies. The indoor air temperature measurements were conducted in seven classrooms in two schools constructed in 1960 and 1990. These measurements are used to calibrate the building simulation models of these schools. The study's results show that, in the current extreme year, classrooms on upper floors with larger window-wall ratios WWR (60%) and lower thermal building envelope properties are at a higher risk of overheating. Conversely, in classrooms located on lower floors, or featuring a small WWR (10%), or better thermal properties, no other Climate-resilient measures are needed. Under extreme future years the external roller blind shading, night cooling, and cool roof measures will be necessary for both schools, particularly for last-floor classrooms with south orientation and a 60% WWR in 1960 building.

A cross-climate assessment of the visual and energy performance of flexible photochromic films for in-situ window retrofits

Driven by their low thermal resistance and static transmittance to solar radiation, existing static clear windows are often considered the least-efficient components in the building envelope, driving the heating and cooling demands and compromising the thermal and visual comfort of building occupants. Hence, window retrofit technologies that utilize innovative coatings are critical for enhancing energy efficiency and indoor daylight quality in the existing building stock. In particular, dynamic photochromic window films that reversibly modulate solar gains responding to the abundance of ultraviolet radiation are promising but received little attention. In this paper, five commercial flexible photochromic window films were experimentally characterized, and their energy and daylighting performance were numerically and parametrically evaluated in a representative office with different window configurations and orientations across six representative cities with a diverse range of climates. This is one of the first works dealing with photochromic window films as a retrofit technology. The results show that the films exhibit excellent colour-rendering and cyclic stability with rapid switching/bleaching rates. In addition, annual energy savings in the 1% − 4% range were observed for low window-wall ratios, reaching 10% − 14% in cooling-dominated climates with lower latitudes using PC-1, which resulted in the most significant cooling energy savings. Although the film influenced the quantity of light, resulting in lower daylight autonomy, improvements in the useful daylight illuminance and significant reductions in discomfort glare levels were the major benefits of retrofitting existing double-glazed clear windows with the photochromic film.

Building energy consumption optimization method based on convolutional neural network and BIM

The increasing tension of energy supply and demand makes the optimization of building energy consumption more and more concerned by researchers. Based on the theory of convolutional neural network and BIM (Building Information Modeling), a building energy consumption optimization model is constructed. The optimization parameter solving problem of convolutional neural network is solved. In the simulation process, a calculation model of the same size as Revit's three-dimensional model is established in eQUEST software, and the basic analysis parameters of the model, such as geographical location, meteorological data and other information, component materials, and running time table are set as unified standards. The energy consumption simulation analysis was carried out for the self-built model and the model automatically generated by the improved DOE-2 file in eQUEST software. The body coefficient of the building is 0.370, and the window-wall ratios in the east, west, south and north directions are 0.07, 0.21, 0.30 and 0.16, respectively, which all meet the requirements of relevant specifications. Compared with the scheme before optimization, it is found that building energy consumption is reduced by 24.53%, natural lighting is increased by 18.98%, and natural pressure par hours are increased by 10.57%.

Impact of Window-to-Wall Ratio on Lighting Load in Municipality Building-A Case Study of Bharatpur Metropolitan Administration Bloc

Visual comfort is a critical aspect of indoor environments, contributing to occupant satisfaction, well-being, and overall productivity. In the face of rapid urbanization, particularly in regions like the Chitwan District, understanding and enhancing visual comfort in built environments take on heightened significance. The primary focus of this study is to explore how varying Window-Wall Ratios (WWR) affect the energy performance of buildings. The research begins with an in-depth review of existing literature on building energy efficiency, focusing on the significance of WWR in determining natural lighting penetration. Field measurements are collected to establish a baseline understanding of the building's lighting performance. Utilizing advanced simulation tools, the study explores various WWR scenarios to simulate the potential impact on lighting load. The analysis considers both energy efficiency and occupant comfort, aiming to identify an optimal WWR that balances natural lighting benefits with energy conservation goals. The study finds that a 30% WWR represents the ideal balance for effective electricity consumption for lighting. Monthly analysis underscores its significance by revealing diminishing returns beyond this point. Consequently, recommended optimal WWR values stand at 25% for the ground floor and 30% for both the first and top floors. The findings hold significant importance for designers and policymakers in making informed design and policy decisions.

Alternative window wall ratio of glasses with different solar heat gain coefficient and solar transmittance and their effect on total energy consumption in alternative directions

Energy simulation model of the building of Eskişehir Technical University Industrial Engineering Department Academic and Administrative Staff rooms were created in this study carried in the scope of energy efficiency and performance of buildings. In the aforementioned energy simulation mode, in line with the International Measurement, Verification and Energy Needs Standards and Protocol (IPMVP) “energy consumption verification”; heating energy, indoor-outdoor environment and climate data were defined, energy consumption verification was carried out and a realistic model was achieved. Using the realistic model achieved, alternative directions were applied to alternative window wall ratios thereby calculating “reference energy consumptions” in “reference building models”. Energy consumptions, calculated by applying alternative glass types to reference models, were then compared with reference energy consumptions

Energy modelling and saving potential of polymeric solar-responsive thermochromic window films

Windows are often considered the weakest components in the thermal envelope driven by their low thermal resistances and static transmittances to solar gains. While low-E coatings improve the former, climate-responsive coatings that adjust their thermo-optical properties in response to changing boundary conditions are promising to address the latter. In particular, thermochromic films are passive technologies that rely on intrinsic material properties to adapt to varying ambient conditions and are more accessible with simpler structures than their active counterparts; hence, they prevail for solar control applications. However, the nature of current building energy simulation tools imposes limitations on evaluating their performance. In this article, a 1-D transient heat transfer model was developed in MATLAB/Simulink to evaluate the annual heating and cooling energy performance of thermochromic glazing while overcoming several limitations of current building energy simulation tools by accounting for spectral-selectivity, gradual transmittance change, hysteresis behaviour, and delayed switching time. The model was benchmarked against EnergyPlus, and the annual energy performance of a representative room was then evaluated for several double-glazing configurations, window-wall ratios, and exposures in the cold and hot climates of Toronto, ON and Abu Dhabi, UAE, respectively, while quantifying the effects of varying the hysteresis width and switching time. The results showed that commercial thermochromic glazing outperformed clear and low-E windows for both climate conditions. In particular, for a window-wall ratio of 80 % and compared to clear reference glazing, annual energy use intensity reductions up to 6.3 kWh/m2 and 12 kWh/m2 were realized in Toronto and Abu Dhabi, respectively, utilizing a glazing configuration that combined exterior thermochromic and interior low-E coated panes, where the latter helped in increasing the former’s temperature causing it to switch at lower ambient temperatures.. While the typical 30-minute switching time of thermochromic coatings was found to increase the annual energy use intensity by up to 0.5 kWh/m2, a 5 °C hysteresis reduced the annual cooling energy use intensity by up to 0.2 kWh/m2 in Abu Dhabi. Less significant effects and savings were found for lower window-wall ratios, particularly in Toronto, where the coating rarely reached temperatures higher than 45 °C.

Optimized design and energy consumption simulation of window-wall ratio in Yanqui Library, Jimei University

The size of the window-to-wall ratio is a key factor affecting the natural lighting, ventilation and energy consumption of a building. Taking the Yanqui Library of Jimei University as the object and combined with different shading conditions, the range of window-wall ratios that simultaneously meet the requirements of natural lighting and energy saving is derived by using Revit, Ecotect and PKPM software simulations around lighting, energy consumption and natural ventilation. The main conclusions are as follows:(1) With the use of external shading, 0.53 is the maximum window-to-wall ratio for west-facing rooms to meet lighting and energy-saving requirements. (2) The window ratio in the west room is not greater than 0.38, and the north-south room is not greater than 0.55, and the average indoor wind speed in the transitional season is not greater than 0.5m/s.

Using artificial neural network and WebGL to algorithmically optimize window wall ratios of high-rise office buildings

Abstract By coupling parametric modeling, building performance simulation engines, and optimization algorithms, optimal design choices regarding predefined building performance objectives can be automatically obtained. This becomes an emerging research topic among scholars in the fields of architecture and built environment. However, it is not easy to apply this method to real building design projects, because of two main drawbacks: Building performance simulation is too time consuming, and the numerical visualization of final results is not intuitive for architects to make decisions. Therefore, this study tries to fill these two gaps by training an artificial neural network to replace simulation engines and developing a web application to speed up the 3D visualization of selected design choices. These two strategies are applied to optimize office towers’ window wall ratios in Hangzhou, China. Architects working on new design projects in that city can obtain the optimal group of window wall ratios for four facades in 2 s, faster than using simulation engines, which cost architects 2 weeks. Moreover, architects can also efficiently observe the appearance of design solutions with the web application. By improving its usability from these two aspects, this study significantly improves the applicability of algorithmic optimization for building design projects.

Calculating urban heat demands: An analysis of two modelling approaches and remote sensing for input data and validation

Building stocks account for a large share of energy consumption and harbour great potential for reducing greenhouse gas emissions. The field of urban building energy modelling (UBEM) offers a range of approaches to inform climate protection policies, producing output of different granularity and quality.We compare two typology-based (archetype) approaches to urban heat demand calculation in a mixed-use area in Berlin, Germany. The goal is to show challenges and pitfalls and how remote sensing can improve the modelling. The first approach uses 2D cadastral data and specific heat demand values from a typology. For the second approach, we derive a 3D building model from aerial imagery, use parameters from the same typology, and calculate the heat balance for each building. We compare the differences in several geometric parameters, U-values and the heat demand. Additionally, we analyse if window detection on aerial image textures and surface temperatures from aerial infrared thermography can improve the estimated window-wall ratios and U-values. The two heat demand approaches lead to different results for individual buildings. Averaging effects reduce the differences at an aggregated level. Remote sensing can be used to improve some geometric parameters needed for modelling, but still requires additional research regarding U-value estimation.

The Optimum Performance of Building Integrated Photovoltaic (BIPV) Windows Under a Semi-Arid Climate in Algerian Office Buildings

Recently, Building Integrated Photovoltaic (BIPV) windows have become an alternative energy solution to achieve a zero-energy building (ZEB) and provide visual comfort. In Algeria, some problems arise due to the high energy consumption levels of the building sector. Large amounts of this energy are lost through the external envelope façade, because of the poorness of the window’s design. Therefore, this research aimed to investigate the optimum BIPV window performance for overall energy consumption (OEC) in terms of energy output, heating and cooling load, and artificial lighting to ensure visual comfort and energy savings in typical office buildings under a semi-arid climate. Field measurements of the tested office were carried out during a critical period. The data have been validated and used to develop a model for an OEC simulation. Extensive simulations using graphical optimization methods are applied to the base-model, as well as nine commercially-available BIPV modules with different Window Wall Ratios (WWRs), cardinal orientations, and tilt angles. The results of the investigation from the site measurements show a significant amount of energy output compared to the energy demand. This study revealed that the optimum BIPV window design includes double-glazing PV modules (A) with medium WWR and 20% VLT in the southern façade and 30% VLT toward the east–west axis. The maximum energy savings that can be achieved are 60% toward the south orientation by double-glazing PV module (D). On the other hand, the PV modules significantly minimize the glare index compared to the base-model. The data extracted from the simulation established that the energy output percentages in a 3D model can be used by architects and designers in early stages. In the end, the adoption of optimum BIPV windows shows a significant enough improvement in their overall energy savings and visual comfort to consider them essential under a semi-arid climate.

A metamodeling method to study the nonlinearity of building thermal behavior

Understanding the nonlinearity of the thermal behavior of buildings is important for their design and energy analysis. This paper presents a method for the study of the nonlinearity of building thermal behavior based on a metamodel for cooling energy needs. Four measures were introduced to assess nonlinearities using the metamodel coefficients. We studied the nonlinearity of the thermal behavior of an office. A higher metamodeling accuracy was generally obtained for hot climates, high internal heat gains and lightweight thermal mass. Conversely, the nonlinearity of thermal behavior was accentuated in cold climates and with low internal heat gains. The nonlinearity measures were strongly associated to the mean outdoor air temperature in fifteen typical European climates using power laws, with R2 ranging from 0.75 to 0.96. They were also strongly associated to internal heat gains (R2 > 0.96) in the coldest climate, but low and almost stable in the hottest climate. Moreover, the interactions between the building components were more influential on cooling energy needs than quadratic behavior. A metamodel giving energy needs as a function of the physical and geometric parameters was derived. Its extrapolation with various window-wall ratios generally gave an acceptable accuracy, with quadratic variation of the errors. We propose a classification of building thermal behavior into three regimes: highly nonlinear when the energy needs are close to zero; intermediate with decreasing nonlinearities that can be expressed by power functions; and finally, a quasi-linear regime with almost-steady nonlinearities.

Solar Strategies for net-zero energy housing in Canadian North

The North imports most of its energy for fuel and cost of fuel is much higher than the national average, consequently, cost for space heating relying on fuel is very high. The North has an abundance of solar energy available. With the growing concerns on climate change, the region desires to be less dependent on fossil fuels. Significant energy savings for little added cost in housing could be achieved by building high performing envelope systems and integrating solar design strategies. The objective of this paper is to investigate the potential of integrating solar design strategies in improving energy efficiency of housing suitable for the Canadian Northern climates through modelling by optimizing passive solar design and optimal use of thermal and electrical energy from Building Integrated Photovoltaic/Thermal system (BIPV/T) to achieve net-zero energy housing. A reference home with typical construction built in Northern region is modelled using EnergyPlus. The key solar design strategies and building envelope parameters are optimized to minimize energy consumption and maximize the energy production for the reference home. The parameters investigated include thermal resistance of building envelope components, window-wall ratios, thermal mass, night window shutters, shading schedules, and ventilation rates. The optimal use of thermal energy produced by BIPV/T system by integration with Heat Recovery Ventilation (HRV) and air-source Heat Pump (ASHP) is evaluated. Modelling results show that 43% energy saving can be achieved by optimizing the passive solar design and overheating can be eliminated by proper solar shading and natural ventilation. The integration of BIVP/T with HRV can reduce the frost cycle by 10.4%. These preliminary findings demonstrate the potential of integrating solar design strategies to reduce energy consumption and develop net-zero energy housing for the Canadian North.

Study on the Optimal Window and Wall Ratio of Village and Town Housing Based on Energy Consumption

Compared with the cities, the villages and towns have greater space, more flexible layout, more abundant resources. we should make full use of the villages and towns’ environment and resources to create a comfortable indoor and outdoor environment for villages and towns. In the face of the hot and wet environment of village and town house and the poor outdoor wind environment, this paper focuses on improving the performance of village houses in the aspects of the window wall ratio. Through theoretical derivation and numerical simulation of different window-wall ratios, we derive formulas for the ratio of energy dissipation to window-wall ratios of buildings, and finally get the optimal window-wall ratio of the house.

Modified Split Flux를 이용한 주광률 계산식 적용에 관한 연구

Daylighting has a great effect on people inside the room. It is also closely related to the lighting energy consumption. Daylight factor(DF) is a very important index for evaluation of the daylighting in overcast sky. The objective of this study is to verify the suitability of the Tregenza`s Modified Split Flux formula for the calculation of the daylight factor. We compared the daylight factors calculated by two methods; one by a measurement with 1/5 scale model and the other by the Daysim program. We used variables for verification as window wall ratios(WWR) and angles of the sky visible. As a result, daylight factor calculated by Modified Split Flux is similar to the measurement when more daylight enters the inside. And error is significantly increased when the angle of the sky visible is .

Experimental Study on Discharge Coefficients of Windward Window in Buildings with Wind-Driven Cross Ventilation

Focus on the prediction of flow rates in buildings under natural ventilation, the investigation conducted a series of model rooms with cross ventilation. The impact of window-wall ratios, windows configurations as well as corresponding flow rates was investigated. The object of this investigation is to analyze characteristics of windward window opening discharge coefficient by measuring static pressure difference and the flow rate through windows. The conclusion are as follows: For large openings, the discharge coefficient of windward window opening increases as the window-wall ratio grows up; With windward window-wall ratio of 44.4% and 11.1%, the discharge coefficient of windward openings is almost irrelevant to flow rate and less affected by leeward window area; However, with windward window-wall ratio of 2.78%, the discharge coefficient increases slightly as flow rate rises, and the larger the area of leeward opening is, the smaller the discharge coefficient of windward opening becomes.

Design configuration for a higher efficiency air conditioning system in large space building

The full air conditioning and the stratified air conditioning designs in large space buildings were investigated based on air flow measurement that pertains to an in-patient hall of a hospital building. We compared and analyzed the indoor comfort parameters such as temperature and air velocity. On the basis of the measurements, we calculated the theoretical load index by solving the model for inner surface temperature of the building envelope based on the modified radiant heat transfer method. Using flow fields and parameters that are generated by computational fluid dynamics (CFD), the indoor thermal comfort when adopting the full air conditioning and the stratified air conditioning designs can be effectively analyzed. And the respective energy saving rate of the two air conditioning design loads in the hall at different storey heights, window-wall ratios, and air supply heights can be compared. Finally, the recommendation for usage of the stratified air conditioning design was put forward in large space buildings.

Evaluation of fenestration specifications in Egypt in terms of energy consumption and long term cost-effectiveness

The Egyptian Residential Energy Code (EREC) provides specifications and recommendations for the construction of buildings that aim to provide comfort built environment for the occupants. Among these specifications are many dependency relationships between different variables that affect the selection process of the building fenestration. The effect of these variables (window–wall ratio and glass thermal properties) and their associated shading devices (recommended by EREC) on the optimization of energy consumption, as well as its long-term cost-effectiveness, is the main focus of this paper, investigated in three climatic zones in Egypt, under different climate change scenarios. Although these specifications are well-defined in EREC, recommendations of the best combinations of these variables (for each climatic zone) do not exist. The findings recommend different combinations of window wall ratios, glass types and associated shading devices according to each climatic zone, to achieve indoor thermal comfort, as well as long-term cost-effectiveness.

Parameter Analysis on Energy-Saving Behavior of a Steel Residential Building

The steel residential building has been widely used for its good seismic performances. In order to study the energy-saving behavior of the existing steel residential building, an on-site test on envelope structure of a typical steel building in cold region is conducted. Based on that, a simplified numerical model is established in which dynamic energy theories, solar radiations and indoor thermal disturbances are considered. The model is verified through testing data. Parameter analyses including 6 series sum up to 38 models are carried out on 6 main influential factors. The results show that improving thermal behavior of building envelope, adopting flexible sunshade schemes in different seasons, using even and simple building configuration and adopting different window-wall ratios for windows with different orientation are effective ways to decrease the energy consumption of buildings. The thermal design recommendations for steel residential buildings are also produced.

Impact Analysis to Building Energy Consumption of Daylighting Combined Lighting Control

A study on the building energy consumption analysis of daylighting-based lighting control strategy was carried out. A circle type of building was mainly simulated by using the eQUEST energy simulating software. By setting various window-wall ratios, we try to find the relationship between the energy saved by daylighting-based lighting control and the other main energy consumptions, such as the cooling and heating energies. The data shows that the energy saving potential of daylighting-based lighting control strategy can be 40% under the proper window-wall ratio, and in the meanwhile, the total energy saving of the whole building can be 8%. A formula is given to get the best window-wall ratio of various cities according to its geographical information and local climate factors.