Assessment Of Discomfort Glare Research Articles

Daylighting performance and discomfort glare assessment of granular aerogel glazing system: A full-scale comparative experiment

Energy saving, natural lighting, and visual comfort are essential factors to be considered in window design. Granular aerogel glazing system (AGS) has great energy-saving potential, whereas the studies on daylighting performance, especially the visual comfort of AGS are very limited. In this study, a full-scale experiment was conducted to evaluate the daylighting performance and discomfort glare of AGS compared to that of the double-glazed system (DGS) in overcast and sunny days. The horizontal illuminance in the front, middle, and back positions, the vertical illuminance, and the illuminance uniformity were comprehensively analyzed. The high dynamic range (HDR) photograph technique was used and validated. The daylight glare probability (DGP) and daylight glare index (DGI) identified by the task area method, threshold method, and factor method were extracted from HDR images by Evalglare. The results showed that the average horizontal illuminance in the AGS test room is lower than that in the DGS test room. However, due to the scattering effect of AGS, the horizontal illuminance of the AGS test room may be higher than that of the DGS test room in positions where no direct sunlight directly hitting at noon in sunny days. The maximum increasing rate of the hourly horizontal illuminance in the middle and back positions of the AGS test room in September is 37.8% and 54.5%. It is also found that glare may occur in the AGS test room mainly due to excessive luminance. The discomfort glare in the AGS test room may be intolerable in sunny days.

In-situ evaluation of high-performance glazing based on illuminance and glare

High-technology glazing panes are designed to meet the need for natural light, while optimizing key functions such as reducing solar heat gain in spaces and/or redirecting daylight to the rear of the spaces. However, the actual performance in terms of both illumination and glare protection of these glazing systems is often unknown. This study aims to compare the visual comfort performance of four complex fenestration systems by means of point-in-time measurements under real sky conditions and for different seasons. The tested systems included: two glazing types with embedded seasonal solar protection, namely, MicroShade™ and Coolshade™, one prototype of daylight redirecting glazing with embedded micro-mirrors (GEMM), and one clear glazing. We conducted our tests in side-by-side nearly identical spaces in the NEST building in Dübendorf, Switzerland. Results showed a higher daylight provision for clear and daylight redirecting glazing. Discomfort glare assessment from daylight showed that MicroShade™ was substantially more efficient at addressing glare due to sunlight for high sun angles when compared to Coolshade™. The performance of the GEMM prototype was highly dependent on the glazing pane used and one pane provided a promising performance when it comes to mitigating glare risks for high sun positions. However, none of the systems were able to provide an adequate glare protection for lower sun positions. The performed measurements provide a basis for the calibration of simulation models.

EVALUATION OF DAYLIGHT PROVISION AND DAYLIGHT GLARE PROBABILITY FOR DIVERSE WORKSPACE CONFIGURATIONS

ABSTRACTS Office environments can be integrated with particular workspace configurations owing to diverse tasks encountered in these workspaces. This study attempts to discern how effective different office workstation configurations are on daylight performance and tries to quantify this effect by means of a dynamic daylight simulation based approach, depending on the criteria addressed in EN 17037:2018 Standard. The purpose of this study is to explore the impact of workstation configurations on daylight provision and glare protection in workspaces through several configuration setups. In this study, climate based daylight metrics are used for daylight performance determination and assessment of discomfort glare caused by daylighting is performed by Daylight Glare Probability (DGP) index. This study aims to contribute to the growing body of research in the scope of EN 17037:2018 for daylighting in office environments and the obtained results represent the significance of daylighting and visual comfort conditions for diverse workstation configurations.

EVALUATION OF DAYLIGHT PROVISION AND DAYLIGHT GLARE PROBABILITY FOR DIVERSE WORKSPACE CONFIGURATIONS

ABSTRACTS Office environments can be integrated with particular workspace configurations owing to diverse tasks encountered in these workspaces. This study attempts to discern how effective different office workstation configurations are on daylight performance and tries to quantify this effect by means of a dynamic daylight simulation based approach, depending on the criteria addressed in EN 17037:2018 Standard. The purpose of this study is to explore the impact of workstation configurations on daylight provision and glare protection in workspaces through several configuration setups. In this study, climate based daylight metrics are used for daylight performance determination and assessment of discomfort glare caused by daylighting is performed by Daylight Glare Probability (DGP) index. This study aims to contribute to the growing body of research in the scope of EN 17037:2018 for daylighting in office environments and the obtained results represent the significance of daylighting and visual comfort conditions for diverse workstation configurations.

Practical application of HDRI for discomfort glare assessment at indoor workplaces

Unified Glare Rating (UGR) is a measure of discomfort glare at indoor workplaces. Image luminance measuring device (ILMD), as an array photometer, makes it possible to measure the luminance distribution in the form of luminance map. It is the base for UGR calculation by an appropriate computer program. The range of measured luminance depends mainly on a glare source luminance, which often significantly exceeds the abilities of an array photometer sensor. High dynamic range (HDR) method, which is used in photography, can solve this problem partially. A practical approach to this problem was presented in the paper. A new procedure for preparing the set of photos for building HDR images was introduced. This effective method was developed to be used in UGR calculations. The use of the proposed procedure makes it possible to perform UGR measurements reliably, quickly, and efficiently, even by nonexperts in the field of lighting engineering.

조명의 면적 및 조도 연출 변화에 따른 불쾌글레어 평가 연구

조명의 면적 및 조도 연출 변화에 따른 불쾌글레어 평가 연구

An epidemiological approach to daylight discomfort glare

This paper attempts to extend methodologies of analysis derived from medical disciplines into discomfort glare assessment in office environments. Epidemiology is concerned with the occurrence, prevention and control of health-related events in specific populations. Understanding discomfort glare as an occupational risk factor and glare indexes as its diagnostic tests, allowed us to borrow performance metrics developed in the field of Epidemiology to fully characterize the diagnostic accuracy of some of the accepted, albeit imperfect, discomfort glare diagnostic methods. To demonstrate the applicability of this approach, we compared the results of daylight glare index, daylight glare probability, vertical illuminance at the eye, and degree of eye opening with a reference standard from a random sample (n = 45) in three different daylit experimental scenarios. We calculated the sensitivity, specificity, likelihood ratios, Youden's index, and receiver operating characteristic curves. Our results showed an acceptable diagnostic performance of the evaluated daylight glare indexes. We defined a criterion to assess the goodness of any discomfort glare diagnostic method and presented a method to optimize their performance by selecting the proper cutoff point according to specific diagnostic requirements. Finally, we discussed the benefits and implications of the epidemiological approach and explored future research directions in order to improve our ability to predict and asses the occurrence and magnitude of daylight discomfort glare.

Gaze and discomfort glare, Part 1: Development of a gaze-driven photometry

Discomfort glare is a major challenge for the design of workplaces. The existing metrics for discomfort glare prediction share the limitation that they do not take gaze direction into account. To overcome this limitation, we developed a ‘gaze-driven’ method for discomfort glare assessment. We conducted a series of experiments under simulated office conditions and recorded the participants’ gaze using mobile eye tracking and the luminance distributions using high dynamic range imaging methods. The two methods were then integrated to derive ‘gaze-centred’ luminance measurements in the field of view. The existing ‘fixed-gaze’ and the newly developed ‘gaze-driven’ measurement methods are compared. Our results show that there is a significant difference between the two methods. In this paper, the procedure for integrating the recorded luminance images with the recorded gaze dynamics for obtaining gaze-centred luminance data is described. This gaze-centred luminance data will be compared to the subjective assessment of glare in Part 2 of this study.

Calculation of the Unified Glare Rating based on luminance maps for uniform and non-uniform light sources

In Europe, discomfort glare for interior lighting installations is assessed with the Unified Glare Rating (UGR). UGR is valid for a wide range of uniform light sources but the assessment of discomfort glare from non-uniform luminaires with current glare indices is questioned. LED luminaires often exhibit a non-uniform luminance distribution with alternating areas of high and low luminance. With a growing market share of LED luminaires for interior lighting, a better assessment of discomfort glare from non-uniform light sources becomes essential.In the present paper, the UGR formula is calculated alternatively from the luminance distribution. Individual pixels of a luminance map can be considered as individual light sources or they can be combined to form larger sources. For uniform light sources, the UGR is independent of the division of the luminance map. For non-uniform light sources, the UGR value is strongly dependent on the combination of the individual pixels and differences of up to 17.3 UGR units for the same luminaire are obtained. The UGR calculated from luminance maps is compared with the original UGR from the luminous intensity distribution and the UGR developed for small light sources. In conclusion, the assessment of discomfort glare from non-uniform light sources with UGR calculated from luminance maps is questioned.

Evaluation of discomfort glare in the 50+ elderly: experimental study.

The aim of the study was to analyze discomfort glare sensation in subjects aged 50 years and more in comparison with younger subjects (i.e. younger than 35 years of age). The experiments were performed on a computer workstation placed in controlled lighting environment where 2 discomfort glare conditions were modeled. Each participant performed for about 1 h specially designed visual tasks, including the tests with Landolt's rings presented on the screen by a computer program. The glare evaluation method consisted of subjective evaluation of discomfort glare on the semantic glare rating scale, tests of mesopic contrast and glare sensitivity, subjective assessment of lighting quality and asthenopic symptoms. The time needed to perform the task and the number of mistakes were also recorded. The subjective evaluation of glare was compared with the Unified Glare Rating (UGR) index calculated by the DIALux simulation program. A higher percentage of the younger group subjects assessed glare after the experimental session as uncomfortable and intolerable than in the 50+ group, who more often assessed glare as acceptable. The assessment of discomfort glare in the younger group corresponded to higher UGR value compared to UGR value calculated by DIALux. In the 50+ group, such correlation was found only for lower discomfort glare (UGR = 19). The results showed that younger participants more frequently suffered from visual fatigue and assessed lighting as less comfortable. However, the mesopic glare sensitivity increased significantly after the experiments only in the 50+ group under both glare conditions. The obtained results showed that discomfort glare sensation changes with age. The younger population seems to be more sensitive and demanding than the older one in relation to discomfort glare limiting, in spite of the lack of significant objective measures of fatigue. The exposure of the elderly to bigger discomfort glare could adversely affect the objective measures of fatigue like mesopic glare sensitivity and visual performance.

View types and luminance effects on discomfort glare assessment from windows

The use of windows is the most common way of providing natural lighting to interior spaces of buildings. Natural lighting in buildings can displace the requirement for artificial lighting, and thus, has high potential to save energy. Discomfort glare from windows, however, is one of the fundamental barriers to the effective use of natural lighting in buildings. This study examined the potential effects of different window views on the subjective assessment of discomfort glare. Forty-eight subjects (24 men and 24 women) participated in the experiments. The experiment results indicated that the type of view and the distance of the view object are two critical factors of the subjective evaluation of discomfort glare. The results further showed that variations in the luminance distribution of a window (i.e., the ratio of the highest to the lowest luminance of the window) are not a statistically significant factor of subjective discomfort glare, but that there is a significant relationship between the mean luminance of a window and its subjective discomfort glare. This suggests that the mean luminance of a window, the type of window view, and the distance of the view objects should also be considered in the evaluation of the subjective discomfort glare from a window. This paper also discussed the energy-saving potential of daylighting strategies that consider discomfort glare from windows.

Influence of Window Views on the Subjective Evaluation of Discomfort Glare

A window is an indispensable element in a building and acts as a view-giving component that keeps occupants in touch with the outside. This study investigated the potential effect of different window views on the subjective assessment of discomfort glare from a simulated window that rendered blank, natural and man-made views from far to close distances. Forty-eight subjects (24 men, 24 women) participated in the experiments. The experimental results confirmed that the subjective evaluation of discomfort glare can vary with the type of window views presented. The results also indicated that there were noticeable variations in the subjective assessments of discomfort glare over the same visual stimuli. A preliminary criterion for classification of subjects’ sensitivity to glare was illustrated and the difference for the ‘‘glare-sensitive’’ and ‘‘glareinsensitive’’ people was statistically significant. This study found that the psychological factor such as window views could be an important factor in the subjective evaluation of discomfort glare. Widely used glare evaluation formulas such as unified glare rating and daylight glare index would not consider psychological factors. Thus, the finding from this study would contribute to a more realistic evaluation of discomfort glare for future design of glare control systems.

Discomfort glare assessment and prevention for daylight applications in office environments

Discomfort glare from daylight is a common problem in many office environments. It has been the subject of a significant body of research and many attempts have been made to develop reliable assessment and prediction models to address this problem. This paper reviews and discusses the advantages and limitations of using existing glare indices for daylighting conditions. It concludes that available assessment and prediction methods are of limited practical use in daylit situations and currently have no provision for integrated systems that combine daylighting and electric lighting. The paper also presents selected findings from a case study of daylit office environments which identify a number of important design considerations. On the basis of the discussion and the findings from the case study, additional research needs are identified to overcome current limitations. In the meantime, until results from such research are available and can be practically applied, this paper suggests ways to better integrate computer workstations in daylit offices.

Assessment of discomfort glare in motor vehicle lighting

Discomfort glare in motor vehicle lighting has been investigated experimentally using a scale model with stationary test and glare fields. Influences of the size of glare source and age of observer were not investigated Results indicate that the effects of glare illuminance, adaptation luminance, angle of glare and number of glare sources on discomfort glare assessment can be described mathematically. Each parameter was examined individually and the assessments are compared with those obtained previously for disability glare. A general formula is derived which allows the discomfort glare to be calculated for arbitrarily selected combinations of the parameters. The results relate to motor vehicle lighting but are also applicable to street lighting.

A new method for the assessment of discomfort glare

The principles of glare are summarized briefly; the implications of recent research are discussed and a new glare assessment method is described. A glare index is obtained as the sum of only three terms which depend on the luminance, flux fractions and light distribution class of the lighting fittings, and on the dimensions of the room and the reflectances of its surfaces. These terms are easily obtained from graphs given in the paper.