Glare Index Research Articles

Depending on the lighting environment of outdoor sports facilities, A Study on the Impact of Light Pollution.

Light pollution intrusion light due to overuse and misuse of lighting, Urban Skyglow, Glare, Clutter, and Overillumination affect the human body's physiological process, and excessive light mainly causes confusion in night activities. This study suggested a way to reduce light pollution by measuring the vertical illuminance, discomfort glare index(UGR), and glare index(TI) of the residential area for light pollution caused by the lighting environment of outdoor sports facilities adjacent to the residential area. The results of this study are as follows. First, as a result of the illumination simulation, it was confirmed that the reference value according to the KSC illumination standard was met, and the lighting environment of the sports facility has no problem in proceeding with the game. Second, the maximum illuminance value of the vertical plane measured in the window of the residential area barely satisfies the reference value of 10[lx] or less. As a result of implementing it as a way to reduce light pollution, the maximum illuminance value of the vertical plane was measured from 0.94 to 9.82[lx] before improvement to 0.72 to 6.62[lx], and the maximum illuminance of the vertical plane after improvement was reduced by more than 20%. Third, the UGR index of residential area (apartment housing) was satisfied with the international standard of 22, and also satisfied with the domestic Central Environmental Dispute Committee's acceptance limit of 36, so there was no difference between before and after the change. Fourth, as a result of evaluating the unpleasant glare measured in the 500M range of the up and down lines, it was measured as 4.6[%] of the up line and 3.1[%] of the down line, and there was no difference before and after the change as a result of satisfying the unpleasant glare acceptance limit(10%). It is meaningful to use it as light pollution prevention lighting installation data for outdoor sports facilities in the future by presenting supplementary points for the "light radiation permission standard" of the "light pollution prevention method of artificial lighting" according to the lighting environment of sports facilities.

Research on Stray-Light Suppression Method for Large Off-Axis Three-Mirror Anastigmatic Space Camera.

The stray-light suppression of a large off-axis three-mirror anastigmatic space camera has been a hot topic, and this study proposes a composite stray-light suppression strategy that effectively suppresses stray light using the combination of a baffle, retaining ring, and internal antistray light measures. Additionally, the light barrier of the third mirror with a three-layered structure was designed to further optimize the composite stray-light suppression system. At the stray-light simulation analysis stage, in view of the limitations of the Torrance–Sparrow scattering analysis model, an analysis model with wide adaptability is proposed, which can be applied to the stray-light simulation analysis of large-size mirrors with rough surfaces. The simulation results indicate that the point source transmittance of the composite stray-light suppression strategy proposed in this paper is of the order of 10−5 before installing the light barrier of the third mirror, and the veiling glare index of the full field of view is less than 5.8%. After installing the light barrier of the third mirror, the point source transmittance reached the order of 10−8, and the veiling glare index of the full field of view was less than 1.31%. Moreover, the influence of the light barrier of the third mirror on the modulation transfer function of the system was less than 2.3%. The modulation transfer function test of the large-width off-axis three-mirror anastigmatic space camera in a simulated vacuum on-orbit environment was completed, and the test results indicated that the negative impact of the light barrier of the third mirror on the modulation transfer function was less than 3.6%. Moreover, an out-of-field imaging test of the space camera was conducted and the results showed that the image was clear, and the SNR reached 80 dB. The simulation and experimental results prove that the solution in this study can effectively solve the problem of stray-light suppression for large off-axis three-mirror anastigmatic space cameras.

Daylighting evaluation in deep plan office buildings with OPV windows through simulation on Radiance

This research aims to evaluate the OPV window (OPVW) potential application in a deep-plan multi-storey office building, in order to verify its contribution to indoor daylighting quality. OPVW is a cost-effective technology with reduced environmental impact, suitable for application in a multi-story office building due to its potential to adapt to different architectural configurations, lightness and transparency, etc. In an earlier study developed by the authors, an experiment was conducted with a generic office room scale model. Three window materials were compared under real sky conditions (overcast and clear): 3 mm single glass (A scenarios); single glass with OPV (B scenarios); and single glass with application of solar control film (C scenarios). In the present study the same parameters from the experiment were used as input for simulations on Radiance, whose results were compared to previous (work plane illuminance, Daylight Factor and model interior photographs). We found similarities between them. Thus, further results were produced: isolux curves, Daylight Glare Index and render images. The rendered images show a brighter view at A scenarios, and at B and C scenarios. Even if average illuminance is reduced, a better daylight distribution and a reduction in glare are achieved. DGI indicates perceptible glare for some of A scenarios. On the other hand, at most of B and C scenarios, glare was below the perceptible range. Furthermore, the scenarios with OPVW (B scenarios) still show one more advantage: the energy production for artificial lighting when illuminance values are not sufficient.

Adjustable Internal Shading for Home Office Daylighting in Tropical Climates

Home-based workspaces have considerably increased all over the world. Besides, the recent outbreak of the COVID-19 disease forced many people to work from their homes. However, existing residential apartment buildings (ERABs) had been designed for accommodation but not for office works. Low-quality visual environments in ERABs, which have no shading controls on their windows, are evident in tropical climates with extremely high solar radiation. Thus, interior retrofit is significant to provide visual comfort for users in ERABs with low flexibility for modification of their facades. Different interior design variables were simulated by the Radiance-based program to analyse daylighting in a closed-plan room. Before the simulation experiments, field measurement of daylight was performed under a tropical sky to validate the results, and the findings revealed significant Pearson correlations. This paper showed that ERABs are confronting extremely high indoor daylight quantity, up to 10,228 lx, and low quality with intolerable glare. An adjustable model of internal shading, including an integrated Venetian blind with a horizontal light shelf and the window films, was proposed to improve quantitative and qualitative performances of daylighting in tropical regions. This dynamic model could be adjusted to various positions based on daylighting conditions in the buildings. By comparing the simulation results of this model with the base model, indoor illuminance levels could successfully reduce from 32% to 86%; Illuminance Uniformity Ratio (IUR) and Target Daylight Illuminance (TDI) significantly improved up to 180% and 300%, respectively; Daylight Glare Probability (DGP) and CIE Glare Index (CGI) changed from intolerable to imperceptible status. Accordingly, the proposed model can considerably improve daylight quantity and quality in the test room during different times. This study concludes that the dynamic model of internal shadings could provide efficient daylighting, by decreasing the extremely high indoor illuminance and glare in the ERABs in tropical climates.

Behind electrochromic glazing: Assessing user's perception of glare from the sun in a controlled environment

The adaptable transmittance of electrochromic glazing allows to control the solar radiation entering buildings, yet the level of transmittance needed to protect from glare is still an unanswered question. To bridge this gap, this study evaluates the level of visible light transmittance (τv) required for blue-tinted low transmittance glazing to prevent discomfort glare when the sun is visible through the glazing. Twenty participants were exposed to four visual scenarios with varying viewing directions and window transmittance. Results indicate that when the sun is close to the central field of view, a normal-hemispherical transmittance, τv, n-h of 0.6% prevents disturbing glare for most users but does not provide a comfortable situation (this condition corresponds to a “seen” sun disc’s luminance of 4.8 M cd/m2). To achieve comfortable situations, a τv, n-h of 0.14% was found suitable. For non-critical viewing directions, τv n-h of 0.6% is sufficient to achieve visually comfortable space for most participants. This study also examined the reliability of five discomfort glare metrics by comparing their objective output to subjective responses for the tested conditions. The contrast-based metrics (Daylight Glare Probability, CIE Glare Index, Unified Glare Probability, Daylight Glare Index) possess a valid positional sensitivity and show higher Spearman’s rank correlations (ρ – 0.56–0.59) compared to solely saturation-based metrics as the vertical illuminance (Ev) (ρ – 0.44).

A multi-objective optimization design method for gymnasium facade shading ratio integrating energy load and daylight comfort

The large-scale use of curtain walls in stadiums and other public buildings will cause glare and increase the burden of energy consumption, especially in summer. In the early stage of the design, the optimization of the shading devices directly affects the decision-making of the building facade. This research proposes a multi-objective facade optimization method (MOO) for stadium design, using image density atlas (IDA) to provide decision-making basis for facade shading ratio (FSR) optimization in the preliminary design process of gymnasium. In contrast to the traditional design method, the optimized design framework proposed in this study will achieve the balance optimization among contradictory goals of daylight comfort and solar radiation at the same time to optimize the daylighting performance while avoiding glare and reducing energy burden. In this study, a gymnasium in Xiong'an, Beijing was selected as the test case. Researchers took the hourly average illuminance, hourly average solar radiation accumulation, and glare index during the opening hours of the gymnasium in summer (August) as the optimization goals. Then, the genetic algorithm SPEA-2 was used to explore the Pareto frontier solution set of FSR. The optimization scheme FSR = 0.37 is formed through comparison and screening. The research results achieved a 38.5% reduction in DGP, a 54% reduction in solar radiation, and control of illuminance loss within the acceptable range. The case study reveals the importance of FSR optimization to the indoor daylight environment of gymnasium in summer, and how parameter changes affect the rules of various metrics.

Research on a Visual Comfort Model Based on Individual Preference in China through Machine Learning Algorithm

Recently, decreasing energy consumption under the premise of building comfort has become a popular topic, especially visual comfort. Existing research on visual comfort lacks a standard of how to select indicators. Moreover, studies on individual visual preference considering the interaction between internal and external environment are few. In this paper, we ranked common visual indicators by the cloud model combined with the failure mode and effect analysis (FMEA) and hierarchical technique for order of preference by similarity to ideal solution (TOPSIS). Unsatisfied vertical illuminance, daylight glare index, luminance ratio, and shadow position are the top four indicators. Based on these indicators, we also built the individual visual comfort model through five categories of personalized data obtained from the experiment, which was trained by four machine learning algorithms. The results show that random forest has the best prediction performance and support vector machine is second. Gaussian mixed model and classification tree have the worst performance of stability and accuracy. In addition, this study also programmed a BIM plug-in integrating environmental data and personal preference data to predict appropriate vertical illuminance for a specific occupant. Thus, managers can adjust the intensity of artificial light in the office by increasing or decreasing the height of table lamps, saving energy and improving occupant comfort. This novel model will serve as a paradigm for selecting visual indicators and make indoor space be tailored to meet individual visual preferences.

Daylight in Buildings and Visual Comfort Evaluation: the Advantages and Limitations

Exposure to daylight significantly affects the psychological well-being of occupants by diminishing headaches, eye tensions, or stress. Daylight penetration is a matter of collaboration between building façade and perimeter zones that can be controlled through façade design features. This study reviews available daylighting systems to block or redirect natural light inside the space and their overall performance. Adaptation found to be the main key feature of daylighting systems to improve their effectiveness in indoor environments. As the main implication of such systems on the visual comfort performance of occupants, a list of quantitative indices is studied based on their mathematical equation to outline their advantages and limitations. Findings revealed a lack of agreement on acceptable indoor illuminance thresholds for most of the indices and the absence of a reliable glare index in presence of sun within the view field of the occupant. Similarly, many green building certifications propose a specific criterion to assess view out but remained a challenge for future studies.

Stray light separation based on the changeable veiling glare index for the vacuum radiance temperature standard facility.

The vacuum radiance temperature standard facility (VRTSF) is used to determine the temperature traceability of calibration blackbodies accurately for infrared remote sensing. However, the internal surfaces of the VRTSF can emit thermal radiation, which introduces stray light and reduces measurement accuracy. Previously, background subtraction was used to eliminate stray light, without considering dynamic changes in the environment. Therefore, we propose a changeable veiling glare index (CVGI) to evaluate stray light performance based on the concept of the veiling glare index. We analyze the radiation model of the VRTSF system and simulate the attribution of stray light. CVGI can be improved considerably by cooling and by using suitable stop sizes. Experiments performed in the VRTSF show that the CVGI is suitable for analyzing stray light. Using the CVGI, we simulate a method that can significantly reduce stray light in the VRTSF.

Research on the Influence of Light-Controlled Lighting System and Light-Controlled Shading System on Building Energy Consumption Based on Light Environment

The light-controlled lighting system and the light-controlled shading system can adjust the architectural lighting and shading system according to the quality of the indoor light environment, and can reduce the building energy consumption. The energy consumption model of the light-controlled lighting system based on the illuminance of the indoor light control point and the light-controlled shading system based on the uncomfortable glare index for an office building in Wuhan was established respectively by the energy consumption simulation software eQuest. Three key types of glasses were considered to research the indoor light environment. The impacts of the light-controlled lighting system and the light-controlled shading system on building energy consumption were analyzed through simulations.

Transition Planes for Visual Comfort: Out View with Complex Fenestration System Design at Restaurants in Spain

This work deals with daylighting for quality indoor atmospheres, considering building skins. In recent years, almost all retrofit facades of restaurants are highly glazed façades, boosting glare, sun ray absorption and overheating inside. Most of the time, they are not integrated with daylight control; therefore, lighting and out view requirements are not so balanced. Taking into account this daylighting complexity, an alternative façade system is proposed to simulate by Radiance. Previously, perception simulations are compared with measured data, in order to discretize the simulations. In addition, for one point three different view are assessed as: work plane, relation plane and the out plane. Subsequently, two virtual façade models, windows combined by complex fenestration system (CFS) as prismatic film (PF) and highly glazed façade, are tested according to daylighting. For that, three indexes have been used: daylight glare probability (DGP), daylight glare index (DGI) and daylight autonomy (DA). The results show that the proposed complex façade has a good light contribution with less absorption, while maintaining the outside view. In addition, the DGI is needed to test the out plane, because DGP is more suitable for lower luminance; therefore, each visual plane should be assessed regarding different visual comfort conditions, or parameters and methods. Accordingly, the mean DGI result of window combined by CFS is approximately lower in 5% than highly glazed façade. However, the DA of highly glazed is higher in 5%, but the DA of window combined by CFS is enough, above 80%. Definitely, the complex scene at restaurant with the proposed integrated façade system improves light performance and indoor atmosphere.

Disability glare and nighttime driving performance among commercial drivers in Ghana.

ObjectiveGlare caused by the headlights of on‐coming vehicles risk safe driving at night. The study aimed to determine the relationship between glare exposure and nighttime driving performance among commercial drivers in Ghana.MethodsThis cross‐sectional study involved commercial drivers with complaints of nighttime driving difficulties (N = 80; mean age = 41.5 ± 11.1 years). A questionnaire was used to investigate nighttime driving performance following glare exposure. We measured contrast sensitivity and visual acuity under photopic conditions. With an experimental setup in a mesopic setting, we measured visual acuity with and without glare exposure. The difference between the two mesopic visual acuities was quantified as disability glare index. With the same setup, photostress recovery time was also measured. Regression analyses were used to determine the relationship between nighttime driving performance score and the measures taken in both photopic and mesopic settings.ResultsThe average nighttime driving performance score was 47.8 ± 17.5. Driving performance was negatively correlated with all variables (R = –0.87 to –0.30, all p < .01), except contrast sensitivity (R = 0.74, p < .01). A multiple linear regression showed that the model with all variables explained 83.8% of the variance, but only disability glare index was a significant predictor of nighttime driving performance following glare exposure (standardized B = –0.61, p < .01).ConclusionOur results show that the change in mesopic visual acuities following glare can predict nighttime driving performance. This measure can be incorporated into the assessment of driving fitness by licensing departments to evaluate whether a person can drive safely at night amidst glare exposure.

An Investigation of a Modified Formula of Daylight Glare and Limiting Daylight Glare Indices in the Thai Elderly

Discomfort glare is perceived differently by the young and the elderly. However, the existing daylight glare formulae do not take the effects of age into account and the current limiting glare index was obtained from non-elderly subjects. To create lighting suitable for the Thai elderly, especially in terms of glare, two objectives were addressed. The first explored a modified formula of daylight glare for the Thai elderly, while the second investigated the limiting daylight glare index for the Thai elderly in particular areas of residential and public buildings. Both laboratory and field studies were undertaken. The former investigated a daylight glare formula modified for the effect of age of the Thai elderly. Experiments were carried out in a controlled chamber at Kasetsart University, Bangkok, Thailand. The latter explored the limiting daylight glare index for particular areas of residential and public buildings for the Thai elderly with studies conducted in the real environment. A modified formula was proposed to predict daylight glare for the Thai elderly. Limiting daylight glare indices for particular areas of both residential and public buildings for the Thai elderly were also proposed, and the recorded values were found to be higher than the existing limiting daylight glare indices.

Performance Evaluation of Control Methods for PV-Integrated Shading Devices

This study aimed to develop a building-integrated photovoltaic (BIPV) device and optimal control methods that increase the photovoltaic (PV) efficiency and visual comfort of the indoor space. A louver-type PV-integrated shading device was suggested and an artificial neural networks (ANN) model was developed to predict PV electricity output, work plane illuminance, and daylight glare index (DGI). The slat tilt angle of the shading device was controlled to maximize PV electricity output based on three different strategies: one without visual comfort constraints, and the other two with visual comfort constraints: work plane illuminance and DGI. Optimal tilt angle was calculated using predictions of the ANN. Experiments were conducted to verify the system modeling and to evaluate the performance of the shading device. Experiment results revealed that the ANN model successfully predicted the PV output, work plane illuminance, and DGI. The PV-integrated shading device was more efficient in producing electricity than the conventional wall-mount PV systems, the control method without visual comfort constraints was most efficient in generating electricity than the other two with such constraints, and excluding the constraints resulted in less comfortable visual environment and reduced energy benefit. From the results analysis, it can be concluded that based on the accurate predictions, the PV-integrated shading device controlled using the proposed methods produced more electricity compared to the wall-mount counterpart.

Innovative control approaches to assess energy implications of adaptive facades based on simulation using EnergyPlus

The current development of shading systems which respond to both environmental and human inputs; leads to envisioning an envelope that is multifunctional, responsive and dynamic, named as Adaptive Facades (AFs). The key aspect of any external shading system is to control solar radiation that might cause unwanted thermal and visual stresses for occupants which can lead to higher cooling loads significantly. Recent studies attempted to develop non-conventional AFs such as folding structures to fulfill the incapability of conventional systems (e.g. venetian blinds) for delivering multi-objective user demands due to their different design features. Therefore, in this paper motorized venetian blinds were initially used as conventional AFs in Energy Management System (EMS) of EnergyPlus to develop a reference case study. Furthermore, an automatic control was assigned to venetian blinds based on two indoor sensors to control slat angles on hourly basis, Daylight Glare Index (DGI) and task horizontal illuminance. Then, two new control algorithm were derived as hourly transmittance schedule (hTs) and shade factor through extended calculation methods that were used to modify the properties of a roller shade as to take into account the same adjustment of venetian blinds based on indoor sensors. Finally, a comparison was conducted based on annual energy consumption including heating and cooling loads, in which results showed that both methods have discrepancy lower than 6% and can be alternative solutions to evaluate the performance of non-conventional adaptive systems. However, there are several limitations and applicability of the suggested methodologies that were also discussed.

Calidad de la iluminación en las aulas de clase en una Institución de Educación Superior

&#x0D; Objetivo: Determinar la calidad de la iluminación y las estrategias de mejoramiento en las aulas de clase en una institución de educación superior. Metodología: El estudio fue descriptivo, se realizó la medición de la iluminancia en las aulas, así como también la uniformidad de la iluminancia, además se evaluó Índice de deslumbramiento, Índice general de rendimiento del color y temperatura colorimétrica nominal por cada lámpara. Las mediciones ambientales o luxometria se realizaron con un luxómetro marca extech en un total de 15 aulas en las tres jornadas en que se labora. Resultados: la iluminancia en la mañana y tarde cumplen la mayoría de las aulas, contrario en la jornada de la noche en donde ninguna cumple con la norma ISO 8995, además la mañana y la tarde existen aulas con niveles excesivos de iluminación y la noche con niveles muy por debajo de los apropiados, la mayoría de las aulas en las tres jornadas no cumplen con la uniformida, no existe deslumbramiento molesto, así como también algunas lámparas no cumplen con rendimiento del color apropiado, y la temperatura colorimétrica requerida. Conclusiones: Existen aulas que no cumplen con la iluminancia, así como con la uniformidad en las tres jornadas, se resalta que hay un aula que no cumple con tres parámetros, iluminancia, uniformidad y rendimiento del color, esto puede afectar el desempeño laboral y ocasionar molestias y enfermedades en la vista.&#x0D;

Impact of adjustment strategies on building design process in different climates oriented by multiple performance

Adjustment strategies including window ventilation and shading have important improvements in energy consumption, thermal and light environments, furthermore, the upper limit for improvement is affected by design parameters. However, studies incorporating adjustment strategies in the building design process are very limited. To address this research gap, we explore the effects of window ventilation and shading on building design performance from uncertainty analysis, sensitivity analysis, and multi-objective optimization. Furthermore, China’s typical climate zones are compared given climate effects. Results indicate that (1) the uncertainty of total energy demand in the severe cold climate is most affected with the uncertainty increase rate being 32.0%, the uncertainty of thermal comfort ratio in the hot summer and cold winter climate and the hot summer and warm winter climate is most affected with the uncertainty increase rate being 16.3% and 14.0%, respectively. (2) the sensitivity analysis of the thermal comfort ratio is more sensitive to adjustment strategies than to total energy demand. The severe cold climate is more vulnerable than in other climates. (3) when multi-objective optimization is performed with maximum thermal comfort and minimum total energy demand when considering adjustment strategies, the severe cold climate has the greatest energy-saving potential (38.1%) and the hot summer and cold winter climate has the largest potential to improve thermal comfort (17.6%). More importantly, the light environment is within the comfort range from the daylight glare index, the illuminance, and illuminance uniformity ratios.

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.

Study on Daylighting Optimization in the Exhibition Halls of Museums for Chinese Calligraphy and Painting Works

With respect to the light environment of the exhibition halls for Chinese calligraphy and painting works in the museums, the daylighting design in these display spaces have been studied, the key design factors, such as daylighting pattern, and arrangement of exhibits are examined and explored by field trips. Then, the display spaces are divided into diverse categories whose sky light environments are predicted by the demands of exhibits. Under changed daylighting situations, the daylight parameters, i.e., daylight factor (DF) and DF uniformity, discomfort glare index (DGI) and luminance distribution are calculated. Thus, the proper daylighting pattern and elements in the exhibition halls will be decided. The optimization strategies that optimize the parameters of daylighting patterns and elements are presented. The studies have shown that the daylighting quality will improved by the implement of optimal design, and good luminance environment in the calligraphy and painting exhibition halls are obtained.

IDENTIFYING OCCUPANTS' APPROPRIATE SEATING POSITION AND VIEW DIRECTION IN OFFICE BUILDINGS: A STOCHASTIC SHADE CONTROL BASED MULTIOBJECTIVE VISUAL COMFORT OPTIMIZATION

ABSTRACTManually operated solar shades have a significant impact on indoor visual comfort. This research investigates occupants' appropriate seating position and view direction in a west-facing office cell using a previously developed shade behavior model. The non-dominant sorting genetic algorithm (NSGA-II) based Multi-objective optimization was adopted to identify the optimal and near optimal solutions. Daylight and glare index were used as two visual comfort objectives for optimization and robustness of optimization results against shade behavior uncertainty that was analyzed using statistical analysis. Results show that near optimal solutions can be used instead of the optimal one since they provide more flexibility in seating positions while maintaining almost the same visual comfort performance. And thus, the appropriate seating position considering occupants' preference is 1.5m away from the external window with two view directions near parallel to the window for west-facing office rooms.