Discomfort Glare Research Articles

Age-based effects of yellow lenses on discomfort glare from white LED headlights

Age-based effects of yellow lenses on discomfort glare from white LED headlights

Refractive blur’s influence on discomfort glare perception from white LED headlights at night

This study examined the effects of refractive blur on discomfort perception caused by peripheral glare from white LED passing (low)-beam headlights at night. The study compared two levels of binocular blur (+0.50 diopter [D] and +1.00D) against a baseline of optimal refractive correction. Thirty participants (mean age 21.3±1.6 years; range 20–24 years) simulating a driving position assessed discomfort from glare sources (headlights of oncoming vehicles) located at 40 and 20 m distances using the de Boer scale. The study found that, with a blur of +0.50D, discomfort glare from white LED headlights did not significantly differ from the baseline regarding de Boer scores. However, with a blur of +1.00D, de Boer scores significantly decreased, indicating increased discomfort glare compared with the baseline for all distances (P=0.004). These results suggest that refractive blur may contribute to an increased perception of discomfort glare during nighttime driving.

Evaluating Annual Sun Exposure in LEED v4 for Commercial Office Buildings: Inclusion of Annual Glare to Enhance the Occupant Visual Performance and Comfort

ABSTRACT LEED is one of the most widely adopted building benchmarks globally, and it encompasses multiple rating criteria for performance. However, such criteria typically focus on reducing energy consumption and may disregard providing a high level of occupant satisfaction. LEED focuses on a desk height evaluation of Spatial Daylight Autonomy and Annual Sunlight Exposure to predict the daylight availability and probability of glare, respectively, which may disregard an occupant’s visual comfort at eye level. This paper proposes a more comprehensive approach to daylighting performance evaluation in a commercial office space that incorporates Annual Glare – vertical-eye level glare evaluation, in addition to Spatial Daylight Autonomy and Annual Sunlight Exposure. A comparison between Annual Sunlight Exposure and Annual Glare is established to understand the criteria missing in LEED that evaluates discomfort glare and improves the visual performance and comfort of the occupants significantly.

Effects of non-uniform perforated solar screen on daylighting and visual comfort performance

Perforated solar screens are extensively utilized as a shading solution for fully glazed buildings and transparent envelope systems. While uniform perforated solar screens have been traditionally employed, the growing trend towards non-uniform screens highlights their potential to enhance architectural aesthetics through varied perforation patterns on building facades. However, the effects of non-uniform screens in daylighting performance have been rarely investigated. This study aims to assess the effects of non-uniform perforated solar screens on daylighting performance, encompassing daylight availability, uniformity, and annual glare probabilities. A comparative analysis was conducted using simulation studies for eight distinct non-uniform perforation patterns against a uniform perforation scenario. Orthogonal experiment and data envelopment analysis were employed to identify the influential factors and evaluate the overall performance. The results suggest that non-uniform perforated solar screens with specific perforation patterns significantly outperform uniform screens in terms of daylighting performance, at equal perforation ratios. Specifically, two non-uniform prototypes, namely (h) periphery-center and (f) bottom-top, demonstrated exceptional performance. Furthermore, the perforation pattern was identified as the most significant geometrical factor affecting the overall performance of daylighting and glare discomfort. The results of this study may inform the design of perforation patterns to enhance daylighting performance in non-uniformly perforated solar screens. The novelty of this research lies in establishing a framework for evaluating the influence of non-uniform perforation patterns on indoor daylighting and visual comfort.

Glare-based selection of roller shade properties

This paper presents a measurement-aided modeling workflow for selecting roller shade properties that can significantly reduce the risk of glare, using limited BSDF data. The annual visual discomfort frequency, computed from image-based DGP analysis through the year, is parameterized by listed shade properties (openness factor and total visible transmittance) for practical relevance. The method integrates detailed daylight modeling (Radiance 5PM) and light transmission models through roller shades (Radiance aBSDF with PE), a revised analytical transmission model using limited BSDF data, and a process for refining upper bounds of recommended properties. We discuss errors in analytical models for characterizing bidirectional scattering of shades, proper selection of cut-off angles, sensitivity of results to glare criteria and thresholds, and the impact of the peak extraction algorithm and image resolution. The Radiance-aBSDF with peak extraction should be used for materials with a see-through component that corresponds to view clarity index higher than 10 %.Recommended upper bounds of shade properties, graphically illustrated in openness-transmittance 2-D charts, are presented for different locations, orientations and view directions, for dark, medium and light-colored shades in each case. The boundary of recommended properties depends on the balance between contrast- and adaptation-based discomfort glare, determined by the shade properties, climate and orientation. The results were also compared with glare control classes defined in Standard EN 14501 and pronounce the need for new guidelines and standards on climate-based selection of shading properties. Targeted new BSDF measurements and field studies on glare, view and overall daylight quality will improve current models and allow optimal climate-based selection of fenestration products.

Effects of high-speed rail illumination on traffic safety at night in a road-cum-railway section – Implications for the infrastructure design

Intense light from trains can cause glare, affecting the driving safety of vehicles running in the opposite direction at road-cum-railway sections. This study, in particular, examines glare impacts caused by high-speed rail (HSR) illumination on highway traffic driving safety in a road-cum-railway bridge. Field surveys and tests are conducted on the illumination measurement for HSR, and disability and discomfort glare are investigated and quantified, with parameters being calibrated. A simulation-based platform is established and utilised to explore the impacts of HSR illumination on road traffic safety under different horizontal distances and traffic volumes. Different traffic safety risk indicators are utilised to evaluate traffic safety, including time-to-collision (TTC) and weight integrated risk level (WIRL). The results demonstrate that glare, especially disability glare, significantly increases traffic safety risks. The traffic safety of multi-axle vehicles are more negatively affected. The negative effect appears to strengthen with increasing traffic flows and decline with increasing horizontal distance between the high-speed railway and the highway. Anti-glare light barrier installation is an effective way to eliminate the negative effects and appropriate heights of anti-glare barriers are suggested for different horizontal distances.

Evaluating the impact of high-resolution irradiation data on the daylight performance assessment of adaptive solar shading systems

Adaptive solar shading systems offer a dynamic solution to balance daylight availability and glare control in buildings. While building performance simulation methods are useful to understand the potential of these systems to improve daylight conditions in indoor spaces, it is unclear if established practices such as the use of hourly averaged climate data are sufficient to accurately estimate the benefits of adaptive solar shading in real-world conditions. This study investigates how the time resolution of irradiance data in simulation models affects the predicted performance of adaptive solar shading systems. To that end, a series of simulations for models with time resolutions from 1 to 60 min are run, and the results are compared to quantify the variation in daylight metrics between different resolutions. The outcome of this comparison study reveals that while hourly averaged irradiance data generally suffices for daylight performance estimations, it is also likely to overlook short-term periods of glare discomfort that would be present in high-resolution irradiance data. In the context of adaptive shading design, capturing these discomfort periods can be key to providing solutions that achieve specific visual comfort goals. This suggests that the need for high-resolution irradiance data is project-specific, which emphasizes the need for more tailored approaches in the representation of adaptive shading systems in early building design.

Control algorithm for dynamic solar shadings: A simulation study for office buildings based on ISO 52016-3

In 2019, the building sector was accountable for emitting 12GtCO2, equivalent to 21 % of global GHG emissions. To achieve carbon neutrality by 2050, the building sector must change its pace. One of the ways to achieve this goal is through the installation of dynamic solar shadings in buildings. This study focuses on a single office in two locations characterised by a temperate climate: Liège (Belgium) and Milan (Italy). Two control strategies are designed for Venetian and Roller blinds, one with and one without glare evaluation. They both integrate horizontal illuminance, room occupancy, indoor operative temperature and vertical irradiance according to a multi-criteria approach based on ISO 52016-3. The control strategy aims to balance visual comfort, heating, artificial lighting and cooling energy needs and considers user satisfaction by evaluating the shading activation time. The control algorithms are applied and validated on a DesignBuilder shoebox model. Regardless of location, the control strategy that includes glare control improves the user's visual comfort in terms of light quantity and discomfort glare. However, a total annual energy needs increase is registered independently of the shading. Conversely, if glare is not included in the control strategy, control of thermal loads is observed. This work contributed to developing ISO 52016-3 shading control scenarios for offices and is intended for shading producers, solar shading associations, façade engineers, facility managers and the scientific community working on solar shading simulation and analysis.

Comparison of Simulation Methods for Glare Risk Assessment with Roller Shades

Daylight discomfort glare evaluation is important when selecting shading properties. New standards recommend allowable glare frequency limits but do not specify the modeling accuracy required for annual glare risk assessment. Fast simulation tools allow users to perform hourly glare evaluations within minutes. However, reliable evaluation of glare through roller shades requires accurate modeling of their specular and diffuse transmission characteristics, affected by color, materials, and weaving technology. This study presents a systematic comparison between commonly used glare simulation methods against the “ground truth” Radiance ray-tracing tool rpict in terms of hourly daylight glare probability (DGP), hourly vertical illuminance (Ev), and annual visual discomfort frequency. The results are presented for two shade fabrics using light transmission models with and without a peak extraction algorithm (Radiance–aBSDF and Radiance–BSDF) for the specular component. The impact of sky/sun discretization on glare prediction is also discussed. The results show that the Radiance 5–Phase Method (5PM) is superior when modeling direct sunlight and DGP through shades, while other investigated methods (3–Phase Method, imageless DGP, ClimateStudio Annual Glare) are not as robust for that purpose. Users are encouraged to understand the underlying assumptions in the imageless methods to avoid errors when simulating glare, especially due to the contrast effects.

A Multi-objective Optimization of Window and Light Shelf Design in Office Buildings to Improve Occupants’ Thermal and Visual Comfort

In office buildings, an efficient design of windows and using light shelves as a passive design strategy significantly influence the thermal and visual comfort of occupants while enhancing the productivity and health of users. This study proposes a multi-objective optimization for the optimal design of windows and light shelves in office buildings to improve occupants' comfort. Initially, a parametric model was developed using Grasshopper parametric software. Afterward, the Honeybee energy and daylight plugin was employed for simulating thermal and visual conditions, and finally, multi-objective optimization was conducted with the Octopus plugin. This plugin can determine the best solution as a compromise decision for maximizing occupants' comfort. In this paper, an office building in Tehran has been chosen as a case study. The decision variables are window-to-wall ratio (WWR), shading control strategy, viewpoint, the transmission of glass, light shelf length, and light shelf height. The objective functions of the study are the annual average Predicted Percentage of Dissatisfied (PPD) and the annual average Discomfort Glare Probability (DGP). According to the results, the proposed optimization model leads to an 18.5–70.1% and 9.3–57.1% reduction in DGP and PPD indexes, respectively. The study findings provide practical and useful instruction for architects to select optimal specifications of windows and light shelves to develop occupants' thermal and visual comfort in office buildings.

Morphological and Position Factors of Vertical Surface Light Source Affecting Discomfort Glare Perception

Distinguished from conventional lighting, the LED vertical surface light source (VSLS) is directly exposed to human view, and the effects of which form it takes on visual perception are non-negligible. In the current discomfort glare evaluation system, the solid angle and the position index, which represent the relative relation between the glaring light source and human visual field, are not completely applicable for large-area VSLS, and hence are awaiting supplementation and modification. In this study, a physical experimental setup was established to conduct an evaluation experiment on discomfort glare, employing an LED display and white translucent frosted film to simulate vertical surface light sources (VSLS). The experiments were arranged with 21 VSLS shapes (comprising 3 areas and 7 length-to-width ratios) and 11 mounting positions. Subjective ratings and four eye-movement data parameters—namely, the change rate of pupil diameter (CRPD), mean saccadic amplitude (SA), blinking frequency (BF), and saccadic speed (SS)—were collected from 24 participants under each working condition using the Boyce Evaluation Scale and eye tracking techniques. The main results of this study are the following: (a) CRPD is the most appropriate eye-movement index for characterizing VSLS glare perception; (b) The area of the VSLS is the primary shape element influencing discomfort glare. Furthermore, with the same surface area, the lateral view angle (LaVA) and the longitudinal view angle (LoVA) perceived by the human eye also impact glare perception; (c) A functional equation between the VSLS area, LaVA, and LoVA to the borderline luminance between comfort and discomfort (BCD luminance) is fitted; (d) Based on the eccentric angle and the azimuthal angle, a modified position index P’ is proposed to represent the relative position of the VSLS in the visual field, and the ratio function of BCD luminance of the VSLS at non-central positions and the central position is fitted.

The Position Index of Overhead LED Sources Under Different Spectral Power Distributions and Background Luminances

ABSTRACT The position index was developed by Luckiesh and Guth in 1949 and is widely used in discomfort glare models to account for the position of the glare source when predicting the presence and magnitude of visual discomfort. The applicability of this index to modern LED sources has not been evaluated; however, it is of concern due to potentially higher luminance levels of LEDs compared to the sources used by Luckiesh and Guth. Furthermore, the position index of overhead sources beyond 60° above the line of sight has not been quantified. An experiment was conducted using a hemispherical apparatus with LED sources. The position of the light source, background luminance, the spectral power distribution, and anchor (starting luminance level before adjustment) were varied and two procedures were used to determine the position index of these sources. Data from 29 participants indicate that overhead sources located 60° or 80° above the line of sight were detectable and their position index can be quantified. The position index values were found to be higher than those reported in previous studies, suggesting that anchor bias and the small luminance range in previous studies likely influenced their position index values. No differences were found in position index values by spectral power distribution, background luminance, participant age group, or eyeglass wearing. The position index values reported in this study account for range and anchor bias, providing a better estimate that should be incorporated into discomfort glare models.

Optimization Control Strategy for Transition Season Blinds Balancing Daylighting, Thermal Discomfort, and Energy Efficiency

Natural lighting in office buildings is often affected by excessive solar heat gain and discomfort glare, and the transitional seasons are no exception. Therefore, addressing the issue of natural lighting in buildings has always been a challenge in developing shading control strategies. This study designed a model-based calculation method for shading blind control indicators. The method combines existing physical models for sky conditions, solar radiation, heat transfer, thermal comfort, glare, and illuminance calculations and incorporates modifications and additions. Additionally, an equivalent energy-saving model for shading was established. A shading blind control strategy balancing indoor light and the thermal environment with energy savings during transitional seasons was proposed. In transitional seasons, this method can eliminate 100% of glare, reduce discomfort illuminance duration by 81.3% and heat discomfort duration by 87.5% and save 81.3% of lighting energy consumption when air conditioning is used. By comparing the simulation results of an office building in Xi’an with the results obtained from this calculation method, the absolute error percentage was found to be 6.83%, verifying the reliability of the calculation method. Finally, the proposed control strategy was compared with common methods such as no blinds, end-angle control, and fixed-angle control to evaluate its performance in terms of daylighting, thermal comfort, and energy savings. The results showed that the control strategy proposed in this study has significant advantages with respect to various performance indicators.

Melanopsin Stimulation Affects Discomfort Glare in Lighting Environment

Melanopsin Stimulation Affects Discomfort Glare in Lighting Environment

Investigation of influential variations among variables in daylighting glare metrics using machine learning and SHAP

Previous studies have shown the inconsistent performance of various daylighting glare prediction metrics in office daylit-dominated environments. This lack of consensus may stem from a limited understanding of how their component variables contribute to the prediction power reflected on these discomfort glare models. Previous studies predominantly focused on individual variables' linear, independent impact on glare discomfort prediction, neglecting to explore their non-linear and interaction contributions. This study addressed these limitations by evaluating regularly used glare variables using machine learning-based feature selection and SHAP interpretation methods to parse the collected dataset in a subjective survey. By applying different machine learning algorithms and SHAP explainers, we have identified their contribution importance to the prediction of different scales of glare discomfort rating when incorporated into one model and have observed the difference of interaction effects between these variables on predicting glare discomfort ratings. Our findings indicate that vertical eye illuminance, maximal luminance, and window mean luminance exhibit strong prediction power and significant interaction effects on glare discomfort sensations, indicating that they could be the dominant contributors to glare predictive metrics. Contrast effect variables within the field of view had less predictive influence on glare scales when combined with other variables. This innovative approach enables a comprehensive assessment of different variables' influential sequence and interaction consequences when incorporated into the glare prediction model. It facilitates the development of the new glare discomfort prediction model.

A study on the impact of electrochromic glazing on indoor environment

The study investigates the impact of electrochromic glazing on indoor environments, providing valuable insights for the practical application of electrochromic glazing. Three rooms were constructed in Zhangjiakou City, China, equipped with different shading devices (electrochromic glazing, venetian blind, and base case of the glazing with no shading). Through experiments and simulations, the analysis of the overall indoor illuminance revealed that electrochromic glass, in its dark state, effectively reduces the average indoor illuminance while ensuring a uniform distribution of illuminance throughout the space, meeting the specified values for the discomfort glare index most of the time. During nighttime lighting, the average illuminance in room with electrochromic glazing was 42% higher than in the control rooms. In winter, the daily heat supply quantity in room with electrochromic glazing was 4.4%–21.9% higher than in the control rooms. In summer, the heat gain in room with electrochromic glazing was 19.1%–41.8% lower than in room with base case of the glazing. On a sunny day in winter, the room with electrochromic glazing exhibited more stable PMV values compared to the room with base case of the glazing, with a 20% increase in the duration of PMV thermal comfort compliance, but its Percentage of PPD values were inferior to the room with base case of the glazing. In summer, the room with electrochromic glazing outperformed both the room with venetian blind and the room wtih base case of the glazing in terms of PMV and PPD values.

Reducing Glare on Building Facade by Implementing Vertical Greenery Shading – user-sensation vs luminance-measurement

The user of high-rise office building usually feel discomfort glare because of high luminance from glass facade. This experimental research has an objective to find out how vertical greenery can reduce the sensation of glare. Using here a cubicle that represent one person workstation in 2m x 4m x 3.45m dimension with opening from clear glass, WWR 50%. The base case was the condition without vegetation compared to condition with Vernonia elliptica plant LAI 0.75 and LAI 1.5 which implemented as shading. The result found that vegetation LAI 1.5 can reduce luminance 54.3-56.1% compared to without vegetation. The sensation of glare from Uncomfortable becomes Perceptible (for direct light); from Perceptible-Acceptable becomes Imperceptible-Perceptible (for diffuse light). Vegetation LAI 0.75, for direct light, can reduce luminance 35.3-53.6% compared to condition without vegetation. The glare sensation vote becomes Acceptable. Whilst for diffuse light, although the luminance measurement was increase because of the reflected glare from surroundings, the natural aesthetic and green colour of leaves was relaxing, so that the sensation of glare still at the same vote, between Perceptible-Acceptable compared to without vegetation. This result proof that for biotic shading, besides the quantitative, the qualitative variables play the role.

Multi-objective optimization of an anti-reflection AlN/VO2/AlN thermochromic window for building energy saving

The thermochromic smart window has shown potential for building energy saving by regulating optical characteristics according to real-time temperature. However, most existing studies on smart windows were conducted using an annual building energy-saving analysis. However, the ideal performance of a smart window that strikes a good balance between reducing energy consumption, eliminating the discomfort glare, and providing adequate daylight remains unclear. In this study, a novel AlN/VO2/AlN (AVA) multilayer thermochromic glass with improved transmission by using the thin-film interference principle is proposed, and the energy consumption and daylighting performance of the AVA windows are investigated using a multi-objective optimization method, considering different structural parameters in heating/cooling modes. The effect of different optical characteristics of the AVA glass on building energy consumption and the required annual daylight hours within the useful daylight illuminance (UDI300–2000) is analyzed to find out the Pareto frontier of the AVA windows. The Pareto Optimal Solution (POS) shows the best energy-saving AVA window should possess τlum = 0.58 and ΔτNIR = 0.33, which results in a maximum energy saving of 12.13 % for the office. This solution will strike a good balance between reducing energy consumption, eliminating the discomfort glare, and providing sufficient daylight.

Analisis Prestasi Terma Penghadang Suria Luaran Sedia Ada di Kampung Admiralty, Singapura

External Solar shadings have long been designed as an integral part of a building’s facade for functional, aesthetic and privacy reasons. From a functional aspect, it is used to reduce heat and glare, thus helping to improve the thermal as well as lighting quality of the building. In a tropical climate, the yearlong sun radiation, especially those facing the eastern and western building facades with large glazed surfaces may show severe thermal and glare discomfort issues. This paper analyses the impact of the existing shading system of the vertical and horizontal fins and green facades of The Admiralty Village building in Singapore. A thermal imaging camera was used to detect thermal readings from all of the facade’s shading systems. From the result comparison, each facade of the building requires a different shading treatment due to the different sunlight angles. The south facade is best shaded with horizontal shading. East and west facades require shading that blocks sunlight entering at low angles. The north facade can be left unshaded. Green walls with highly dense vegetation perform more effectively than thermal insulation in reducing the cooling load of the building. This study further convinced the need for solar shading devices, especially in the southern facades of tropical countries.

Influence of macular pigment on the sensitivity to discomfort glare from daylight

Understanding the factors that influence the human perception of glare is necessary to properly address glare risks in buildings and achieve comfortable visual environments, especially in the workplace. Yet large inter-individual variabilities in glare perception remain unexplained and thus uncovered by the current empirical glare models. We hypothesize that this variability has an origin in the human retina, in particular in the density of macular pigments present in its central area, which varies between individuals. Macular pigments are known to absorb blue light and attenuate chromatic aberration, thus reducing light scatter. This study presents the outcomes of the first experiment ever conducted in a daylit office environment, in which glare sensitivity and macular pigment density were measured and compared for 110 young healthy individuals, along with other ocular parameters. The participants were exposed to different glare conditions induced by the sun filtered through either color-neutral or blue-colored glazing. In neutral daylight conditions with sun disc in the near periphery, neither macular pigment nor any other investigated ocular factors have an impact on discomfort glare perception whereas glare perception in conditions with the blue-colored sun disc in the near periphery was found to be correlated with macular pigment optical density.