Discomfort Glare Research Articles

The Effect of a Pre-Trial Range Demonstration on Subjective Evaluations Using Category Rating of Discomfort Due to Glare

ABSTRACT Category rating is a procedure commonly used to evaluate visual discomfort due to glare. One recommended step for good practise in a category rating procedure is to use a pre-trial demonstration (PTD) of the range of stimuli to be experienced. However, PTD have rarely, if at all, been used in past research on discomfort glare. In this study, two experiments were conducted to test the influence of the PTD on evaluations of discomfort due to glare. In the first experiment participants evaluated four glare source luminances with, and without, a PTD. The results suggest that using a PTD increased the reported degree of discomfort perceived for the same glare setting, although this may depend on the manner in which the PTD is presented. In the second experiment, participants evaluated four glare source luminances using PTD with three different luminance ranges: the results suggest this had significant effect on discomfort evaluations in that evaluations of discomfort were lower when a higher luminance range was used. Along with other recent studies, these findings suggest a need to derive a more robust procedure for measuring the discomfort due to glare.

Discomfort glare and psychological stress during computer work: subjective responses and associations between neck pain and trapezius muscle blood flow.

Exposure to additional environmental stress during computer work, such as visual and psychological demands, is associated with increased eye and neck discomfort, altered moods, and reduced well-being. The aim of this study is to elucidate further how subjective responses in healthy, young females with normal binocular vision are affected by glare and psychological stress during computer work, and to investigate possible associations between trapezius muscle blood flow and neck pain development. 43 females participated in a laboratory experiment with a within-subject design. Four 10-min computer work conditions with exposure to different stressors were performed at an ergonomically optimal workstation, under the following series of conditions: no additional stress, visual stress (induced as direct glare from a large glare source), psychological stress, and combined visual and psychological stress. Before and immediately after each computer work condition, questionnaires regarding different visual and eye symptoms, neck and shoulder symptoms, positive and negative state moods, perceived task difficulty, and perceived ambient lighting were completed. Associations between neck pain and trapezius muscle blood flow were also investigated. Exposure to direct glare induced greater development of visual/eye symptoms and discomfort, while psychological stress exposure made participants feel more negative and stressed. The perception of work lighting during glare exposure was closely related to perceived stress, and associations between visual discomfort and eyestrain, and neck pain were observed in all conditions. Furthermore, participants with high trapezius muscle blood flow overall reported more neck pain, independent of exposure. Exposure to visual and psychological stresses during computer work affects the development of symptoms and negative moods in healthy, young females with normal binocular vision, but in different ways. The results also demonstrate the complex interactions involved in symptom development and lighting appraisal during computer work. When optimizing computer workstations, the complexity of the field must be taken into account, and several factors, including visual conditions, must be considered carefully.

Split-pane electrochromic window control based on an embedded photometric device with real-time daylighting computing

Well-designed electrochromic (EC) glazing control can improve the energy performance of buildings and visual comfort of occupants in highly glazed buildings. This paper designed and demonstrated a compact integrated EC glazing automation system to control tint states of a split-pane EC window according to variations of sky conditions. The control is based on monitoring the luminance distribution of the sky and real-time lighting computation for a building interior, using an embedded photometric device (EPD). It optimizes tint states of EC glazing to offer sufficient daylight provision and temper discomfort glare for occupants, which potentially mitigates excessive solar heat gain. ’In-situ’ experiments were conducted in a full-scale testbed to demonstrate the daylighting performance under various sky conditions. Experimental results showed 83% of the working time for work-plane illuminance (WPI) and 95% of the time for daylight glare probability (DGP) were constrained in comfort range (WPI∈[500, 2000] lux, DGP ≤ 0.35) by the automated EC glazing (controlled by EPD) under clear skies; 68% of the time for WPI and 94% of the time for DGP in confined range under clear skies with thin clouds; 62% of the time for WPI and 85% of the time for DGP in confined range under partly cloudy skies.

Automated ‘Eye-sight’ Venetian blinds based on an embedded photometric device with real-time daylighting computing

Optimal shading control can improve occupants’ visual comfort and increase energy savings on artificial lighting and cooling loads during warm seasons. A highly integrated automated shading system is presented in this paper. Designed to regulate daylighting according to the varying sky conditions in decentralized applications, it optimizes visual comfort for occupants and maximizes their view outwards. The shading control is based on real-time lighting simulation for a building interior based on sky (and landscape) luminance distribution monitoring. Its lighting simulation quality was validated in a daylighting test module showing a 10% root-mean-square error in both work-plane illuminance (WPI) and daylight glare probability (DGP). Conducted under various sky conditions during summer, autumn and winter, the shading control demonstrated its capability in regulating daylight provision, mitigating excessive solar heat gain, tempering discomfort glare, and maximizing outside view for occupants with minimal delay. The results showed that the WPI was maintained within the range of [500, 2000] lux in 96% of working time under clear skies and in between 79% and 88% of working time under partly cloudy skies. The expected mitigation of cooling loads due to excessive solar heat gain (SHG) was estimated to reach 47% during a warm climate, compared with no shading protection. The automated shading system was also demonstrated to successfully occlude glare due to secondary reflections on specular surfaces from surroundings.

Potential Benefits of PV-Shading System in Office Buildings and Semi-Continental Climate Conditions

Solar PV shading devices are good solutions to control daylight and reduce the unwanted solar gains, while generate electricity at the same time. Since thermal, electrical and daylighting performance competing each other, it is imperative to consider specific design criteria to optimize and allow energy efficient level of thermal and visual performance. In this context, the study focus on the optimum design of PV shading devices for typical office building with high fenestration ratio and climate conditions of Prague. TRNsys simulation environment was used for the evaluation of the power and thermal performance of the PV shadings considering various tilt angles, projection depth and orientations. Ecotect/Daysim software tools were used to evaluate the daylighting performance and lighting energy use. Useful Daylight Illuminance (UDI) and Discomfort Glare Probability (DGP) indices were also calculated for indoor visual comfort analysis according to the design configuration. Results were overall evaluated to reveal the potential energy benefits compared to the non-shaded case. The study serves as a guide for the optimum design of PV shading systems.

Optimization of luminaire layout to achieve a visually comfortable and energy efficient indoor general lighting scheme by Particle Swarm Optimization

ABSTRACT The design of an indoor lighting system for a sustainable building should comply with the recommended maximum limit of lighting power density. The occupants’ visual comfort and visual performance are to be ensured by complying with some mutually conflicting lighting design parameters, such as maintained average illuminance, overall uniformity, and maximum unified glare rating, to the recommended limits. Judicious balance among these multiple conflicting design parameters is a practical design problem. This article aims to address these aspects of indoor lighting design by applying a particle swarm optimization (PSO) algorithm in a developed lighting computation program. The objective function is formulated with maximum or minimum limits for the design parameters recommended by international standards. The effectiveness of the developed program is evaluated by designing an indoor lighting system with commercially available luminaires for an office space that ensures optimized visual comfort, energy efficiency, and initial cost. Optimized results are validated by DiaLux simulation and a maximum deviation of 2.27% is found. Thus, the results show good agreement with DiaLux simulation and significant improvement in the uniformity of illuminance (0.90) compared to the recommended minimum value (0.70) and in discomfort glare (16) compared to the recommended allowable maximum value (19). The developed program establishes the usefulness of the PSO algorithm to optimize the luminaire layout for an indoor general lighting scheme.

Gevo announces breakthrough development of renewable isoprene, a key chemical building block for producing rubber and rubber products

A movable shading device installed on an adaptive façade is able to change the positions of the shades according to the various control objectives (i.e. daylighting, thermal comfort, glare, energy, etc.) of the occupant. Since the key variables and the control method may change according to the control objectives, it is important to determine the hourly states of the shades in consideration of all of these factors. This study proposes a multi-purposes control strategy of adaptive facades for heating, cooling, lighting energy and glare. To depict the movements of the movable shading devices, the operable range is represented by an n number of fixed shade states having constant intervals. The control strategy entails deriving allowable shade states for glare prevention and energy conservation independently and then deriving the intersection range between the two shade state ranges. A case study was performed to verify the changes in hourly shade states and the energy performance of the envelope obtained by applying the proposed control strategy to an adaptive façade having a movable folding type shading device. The results of the case study show that hourly shade states were determined to satisfy the objectives of glare prevention and energy conservation simultaneously based on weather conditions and indoor requirement settings. From the case study, it can be seen that the proposed method can block the entry of direct solar radiation by lowering the unshaded fraction according to whether or not there would be discomfort glare while increasing the view factor in certain sections to promote the entry of diffuse solar radiation into the indoor space during the cooling and heating periods. The results of the case study also show that there can be large differences in the heating, cooling, and lighting energy performance of the building envelope for each orientation depending on the order of priority given to the objectives of the shading control, i.e. the objective of energy conservation only and the objective of simultaneous glare prevention and energy conservation. However, it was possible to effectively reduce the differences in energy proportions by adopting translucent shades.

The effectiveness of light-emitting diode lighting for providing circadian stimulus in office spaces while minimizing energy use

Architectural lighting has traditionally addressed visual performance and horizontal illuminance on the work plane, later focussing on energy efficiency, while only recently paying particular regard to human health outcomes. The present study evaluated the effectiveness of several light-emitting diode lighting strategies for delivering circadian stimulus to occupants of a typical office space while minimizing energy use. The study employed photometric simulations in a typical open-office space, delivering a criterion circadian stimulus of 0.3 to calculation points modelled at the simulated occupants’ eye level. Six luminaire types, two luminous intensity distributions, six spectral power distributions and two horizontal illuminances were evaluated, resulting in 144 unique lighting conditions. Additionally, the study calculated the discomfort glare for selected luminaires with the highest total lumen output, smallest aperture and direct-only luminous intensity distributions at the higher of the two horizontal illuminances (500 lx). The most impactful strategy involved supplementing common overhead lighting with a desktop luminaire delivering light directly to the simulated office occupants’ eyes, which provided greater circadian stimulus and used less energy than overhead luminaires that were capable of delivering the criterion circadian stimulus of 0.3.

Study on the overall energy performance of a novel c-Si based semitransparent solar photovoltaic window

This paper introduces a novel c-Si based building integrated photovoltaic (BIPV) laminate. It was produced by cutting standard crystalline silicon solar cells into narrow strips and then automatically welding and connecting the strips into continuous strings for laminating between two layers of glass. The overall energy performance of the BIPV insulated glass unit (IGU) including power, thermal and daylighting performance was investigated experimentally. The daily energy conversion efficiency of the active solar cell area was about 15% on sunny days, but it was less than 12% on cloudy days and overcast days. Due to the combined effect of both the semi-transparent PV laminate and the insulated glass unit, the solar heat gain coefficient (SHGC) of the BIPV IGU was as low as 0.25, which was much lower than commonly used glazing windows. Daylight analysis by means of high dynamic range (HDR) cameras and daylight glare probability (DGP) indicated that the BIPV IGU could reduce discomfort glare to some extent compared to clear glass windows. The net energy production of the BIPV IGU was estimated without considering the differences in HVAC energy use in this study. The artificial lighting energy consumption was about 431 W h/day while the average BIPV electricity production for the same period was 1940 W h/day. The net power generation was therefore 1509 W h/day for this BIPV IGU in Berkeley, California. Shading tests for the BIPV IGU were also conducted and the results revealed that the vertical configuration of solar cell wiring in the BIPV laminates was much more sensitive to horizontal shading patterns than vertical shading models. Thus, if shading was unavoidable in some cases, a reasonable arrangement of PV strings should be considered to bring down the energy loss as much as possible. Also, the impacts of environmental factors on the energy conversion efficiency of BIPV IGU were analyzed. Specifically, the power output declined by 0.42% of the peak power for each Celsius degree temperature rise. Thus, if more attention was paid to the heat dissipation issue of BIPV IGU, the overall energy conversion efficiency would be improved.

Stimulus range bias leads to different settings when using luminance adjustment to evaluate discomfort due to glare

Luminance adjustment is widely used to evaluate discomfort due to glare. This paper reports an experiment conducted to investigate two factors of the luminance adjustment procedure, stimulus range bias and direct vs indirect control. Stimulus range bias describes the influence on subjective evaluations of the range of stimuli available to the test observer, with range being the minimum and maximum available glare source luminance in the current context. For the glare source, an artificial window, there were three ranges, having maximum luminances of 5 106, 7288 and 9469 cd/m2. The results suggest that luminance range had a significant effect on settings made, sufficient to change settings by an amount equivalent to one step of a Hopkinson-like discomfort sensation scale. The mean luminance associated with just intolerable discomfort with the low range was less than that associated with just uncomfortable with the high range. Past experiments have used direct control, where the observer makes the adjustment directly, and indirect control, where the observer instructs the experimenter to make the adjustment actions. Both methods were used in the current experiment. It was found that range bias was larger when using direct control than with indirect control. These findings contribute to an understanding of why different studies of discomfort glare have reported different results and hence proposed different discomfort models.

Response to White Light Emitting Diode Aviation Signal Lights Varying in Correlated Color Temperature

Airfield lighting for runways and taxiways is currently undergoing a transition from filament-based incandescent sources to light emitting diodes (LEDs). Although models to assess the relative brightness, discomfort glare, and peripheral detectability of signal lights such as those used for aviation exist, their applicability to white LED airfield lighting has not been verified independently. A series of three experiments was conducted to compare white LED sources, having correlated color temperatures of 2,700 K and 5,900 K, in terms of their relative brightness, discomfort glare, and peripheral detectability. The perceived brightness and discomfort glare from the light sources closely matched predictions from the published models, demonstrating the usefulness of these models at characterizing these responses in airfield lighting. In the case of peripheral detectability, there was little to no difference in how quickly the two LEDs were perceived at low light levels, suggesting that there is no need to consider spectral differences between light source spectra for this response when the intensities are similar to those used in the present study.

Multivariable Optimization of Dynamic Translucent Solar Screen on West-Facing Offices

Discomfort glare frequently occurs in the west-facing rooms of office buildings during the afternoon. Using conventional opaque and fixed solar screens can obstruct the direct solar radiation, and reduces the glare. However, they may considerably reduce indoor daylighting levels and block the view outside at the same time. Thus, dynamic translucent panels are proposed in this study as external solar shading screens on the west-facing facades. Most importantly, a systematic method is developed to optimize the positions of the panels, addressing both daylighting, glare and view. The optimization algorithm - Artificial Neural Networks, combined with daylighting performance simulations is used to determine the optimal design parameters of the proposed solar shading screens. An office room in Guangzhou is used as a case study to test and optimize the proposed method. The whole study process consists of three steps: simulation, regression, and optimization. The results show that the neural network regression results are very close to the simulation ones. It means that deep neural networks can achieve a relatable regression performance and reduce the optimization time significantly. The optimal positions of the solar screens effectively reduce the glare level and maintain a relatively high indoor daylighting level and a large view field. Furthermore, this study also discusses the different effects of the weights for evaluation indicators on the final optimization results.

Qualitative and quantitative analysis of discomfort glare due to artificial indoor lighting

The research evaluated the effect of the change in position of the observer and luminance of light source on discomfort glare. There were two approaches taken in this study, one was qualitative and other was quantitative approach. The quantitative approach was based on unified glare rating. In this study, 11 experiments have been conducted to get degree of glare at different places of room. The qualitative analysis performed over 15 participants and on the basis of questionnaire, degree of glare has been evaluated. A participant has to answer that he finds particular field of direction comfortable or not by marking it on a scale (De-Boer) of 1-4. The result obtained from both approaches was compared to get the comfortable range of illuminance and the angle between the luminaire with line of sight.

Qualitative and quantitative analysis of discomfort glare due to artificial indoor lighting

The research evaluated the effect of the change in position of the observer and luminance of light source on discomfort glare. There were two approaches taken in this study, one was qualitative and other was quantitative approach. The quantitative approach was based on unified glare rating. In this study, 11 experiments have been conducted to get degree of glare at different places of room. The qualitative analysis performed over 15 participants and on the basis of questionnaire, degree of glare has been evaluated. A participant has to answer that he finds particular field of direction comfortable or not by marking it on a scale (De-Boer) of 1-4. The result obtained from both approaches was compared to get the comfortable range of illuminance and the angle between the luminaire with line of sight.

R/G/B/W 4色LED光源不舒适眩光研究

R/G/B/W 4色LED光源不舒适眩光研究

Daylight luminous environment with prismatic film glazing in deep depth manufacture buildings

In this paper, indoor illuminance distributions with a microstructured prismatic film glazing in a deep depth manufacture space were measured. The measured illuminance data with the prismatic film glazing were compared to Radiance simulation results with a conventional glazing. This study shows that using prismatic film glazing at side windows can improve indoor illuminance levels and illuminance uniformity for inner spaces. The technology can work effectively for deep depth manufacture spaces under a clear sky but less effective under an overcast sky for improving illuminance levels and illuminance uniformity. Luminance image and glare metrics were also compared between the prismatic film glazing and conventional glazing. The angle-dependent transmittance properties of light-scattering for the prismatic films with direct sunlight present a different luminance pattern from the conventional glazing with higher peak luminance values but smaller peak luminance areas. In general, the simulated glare metrics with the prismatic film glazing presented lower DGP and DGI glare index than those with the conventional glazing. The time and orientation which may cause high glare metrics and possible discomfort glare with the prismatic film glazing in the deep depth manufacture space are also discussed.

Investigation of an integrated automated blinds and dimmable lighting system for tropical climate in a rotatable testbed facility

Performance of automated blinds and auto-dimming lighting system in providing lighting energy savings and occupant visual comfort was studied in a rotatable testbed facility located in tropical Singapore. The automated Venetian blinds system, consisting of a daylight-redirecting top portion and a glare-controlling bottom portion, was controlled by an in-house developed control algorithm designed specifically for tropical climate of Singapore to introduce maximum daylight while minimising Daylight Glare Probability (DGP). The auto-dimming lighting system used Digital Addressable Lighting Interface (DALI) controller to control T5 fluorescent and LED luminaries. Energy consumption by the lighting system, working plane illumination distribution and DGP were monitored by a network of sensors and high-dynamic range (HDR) camera systems. Compared to non-dimmable T5 lighting, LED lamps provided about 24% of lighting energy savings. Auto-dimming technology showed about 46% lighting energy savings. LED lamps coupled with auto-dimming showed around 80% lighting energy savings. Without window blinds, the working plane illuminance exceeded the recommended 3000 lx level during certain time of the day and DGP exceeded 0.35. The automated blinds effectively eliminated glare discomfort, and with the automated blinds working in conjunction with the auto-dimming, significant lighting energy savings was achieved without compromising the illuminance level at the working plane. 75% of lighting energy savings was achieved for North orientation and 63% for East orientation. Façade orientation was found to have a significant impact on the lighting energy savings potential, with the North orientation achieving higher daylight savings due to higher daylight redirection possibility throughout the day. The lighting energy savings potential is higher for clearer sky conditions due to higher daylight availability. Implementation of daylight re-directing shading system has significant lighting energy savings in the tropics. These lighting energy savings can be captured by deploying an auto-dimming system. With careful design of the system and control algorithm, the lighting energy savings can be achieved while maintaining good visual comfort.

Assessing the effectiveness of dynamic metrics in predicting daylight availability and visual comfort in classrooms

In this study, daylight performance and visual comfort have been evaluated by a longitudinal subjective survey (842 total responses) and simulation-based metrics in four classrooms in two LEED™ silver certified buildings during a year. Dynamic and static daylight and glare metrics are reviewed and critiqued based upon their ability to explain the perception of human subjective responses in classrooms. Results indicate high correlation between students' perceptions and dynamic daylight metrics; sDA300/50% and UDI300-3000/50%, in defining the daylit area. Moreover, according to results the Vertical illuminance-based metrics (sDGPexceed) is more compatible than horizontal illuminance-based metrics (ASE) at fitting the range of perceived discomfort glare. However, more and larger studies are needed to confirm utilizing the sDGPexceed index for indication of discomfort glare in early stage of building design. According to results, daylight and glare metrics' thresholds should be reconsidered based on global filed surveys, since occupants' ability to adapt to higher or lower levels of light is related to culture and climate location.

Discomfort Glare Evaluation using DIALux Lighting Simulation software and using developed Python Program model

Glare is a visual sensation caused by excessive brightness. It is subjective and person dependent. So, it is very difficult to measure glare factor accurately. Glare can be disabling or uncomfortable. Disability glare is the reduction in vision caused by bright light sources and it can be increased with the age of a person. Discomfort glare is a sensation of irritation due to bright light sources. There are various methods to evaluate discomfort glare. These methods are discussed in this paper.
 This paper mainly focuses on two methods of discomfort glare evaluation; Unified Glare Rating (UGR) and Daylight Glare Probability (DGP). These glare factors are calculated by using DIALux lighting simulation software and by using developed program. The experimentation was carried out in two different spaces; Conference room and Optoelectronics laboratory. The values of UGR, daylight factor are calculated by using DIALux and developed program. The comparison of the results obtained is discussed at the end of this paper.

Discomfort glare prediction by using Unified Glare Rating

ABSTRACTGlare which affects comfort or causes distraction is known as discomfort glare and glare which affects the ability to see any object is known as disability glare. Discomfort glare is mainly caused by artificial lighting of the workplace. Discomfort glare can be measured by using Visual Comfort Probability (VCP) or Unified Glare Rating (UGR). This paper discuses the discomfort evaluation methods and presents the calculations of UGR of a specific workplace. The discomfort glare is calculated by using DIALux lighting simulation software, Techno Team LMK measuring system and by using developed Python program model. The results are compared and verified with the feedback received from occupants/users of that workspace. A comparison of the UGR values determined by the DIALux lighting simulation software, LMK measurement system and subjective estimation shows that the values obtained by LMK measurement system are more accurate and are matching with the feedback received from occupants of the workspace.