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Designing the buildings that facilitate optimum utilization of daylight is desirable for its many benefits [1], [2] yet challenging due to other intrinsic properties of daylight responsible for over-heating and discomfort glare [3]. Discomfort glare has been studied for several decades, although current empirical glare models are unable to account for the inter-individual differences in glare perception[4]. The complex and multidisciplinary nature of the phenomenon involves the fields of ophthalmology, lighting engineering, neuroscience but these fields remain quite disconnected from one another, which further adds to the slow progress in understanding this phenomenon [5], [6]. It is, therefore, necessary to incorporate interdisciplinary approach to anticipate what creates or influences the perception of discomfort glare from daylight. We aim to contribute to furthering this understanding by evaluating the discomfort glare perceived by the users in relation to eye morphology, with a dedicated focus on the macular pigment (MP) in the retina (Figure 1), an ocular characteristics shown to influence visual performance [4]. Figure

Although fabrics are widely used as shading devices, reliable simulation models are rather rare and therefore the choice of a fabric with appropriate material characteristics is difficult. This paper presents a simulation model, which can be applied to most of the common available fabric shading materials. Furthermore a comprehensive simulation study has been conducted in order to derive simple to use tables for the selection of appropriate shading properties for a designer. These tables enable the user to select the "right" fabric according to a combination of multiple boundary conditions (location, orientation, window sizes, user positions).

Occupants’ visual comfort in an indoor space strongly depend on the quantity and quality of the daylight inside the space which can be altered with the type of window glazing. In this study, we compared the visual comfort perception of participants with sun in their field of view under two types of glazing: color-neutral and blue-tinted electrochromic glazing. The main experimental variables are the color and visible light transmittances of the glazing. The aim was to determine the influence of these variables on participants’ discomfort glare, view out and color perception. We found that the discomfort glare was perceived more strongly with blue-tinted glazing compared to the color-neutral glazing for a range of (low) transmittances. We also found that the colors of outdoor elements were rated non-natural in case of blue-tinted glazing compared to color-neutral glazing. The outside view was perceived more restricted in blue-tined glazing compared to color-neutral glazing even though both of them maintain view clarity.

A well daylighted space can provide a highly satisfying visual environment. However, if that environment causes us visual discomfort, it can become such a nuisance that we, sometimes literally, turn our backs on this powerful connection to the outside world. Given this, there is enormous value in quantifying the occurrence of discomfort glare within buildings, and in glare models that may guide architects and engineers in design. With the success of climate-based modeling techniques for daylight illuminance, there is now a focus on including discomfort glare metrics in spatio-temporal evaluations. This article conducts a literature review of research focused on spatio-temporal simulations for glare assessment. Studies are reviewed according to their objectives, metrics calculated, spatial scope, temporal scope and scene variety. The goal is to document the limitations of current simulation methods, the potential to generally apply these methods, and how well these methods incorporate empirical glare research. This review finds that, due to computational constraints, there is an over-reliance on illuminance-based metrics for spatio-temporal glare assessment, even while user assessment research reinforces the importance of including contrast-based measures. To achieve an accurate zonal glare assessment, future research should focus on improving simulation efficiency and identifying ways to reduce the spatial, temporal and angular scope of the simulation, while maintaining high accuracy., SDAR Journal of Sustainable Design in Engineering of the Built Environment, 7 (1)

Visual comfort is important to the wellbeing of people and their productivity. However, too much light in the field of view can cause discomfort and disability glare. Under certain conditions it can even cause accidents. This paper addresses the disability glare created by veiling glare and the effect it may have of reducing the visual performance in outdoor spaces. Veiling glare is a particular case when light is reflected off a surface and causes annoyance or impairment of a task to the person in a particular view angle. Two factors that determine the nature and magnitude of veiling reflections are the specularity of the surface being viewed and the geometrical relationship between the observer, the surface and any source of high luminance. Different methods to assess disability glare exist but there is still no clear understanding on criteria to judge an outdoor scenario. A case study where reflected glare form Photovoltaics overlooking a building is of particular concern is presented.

Luminance ratios have historically been used to assess glare. Using data from a previous experiment, this exploratory study investigates the relationship between luminance variations in the field of view (FOV), measured as luminance ratios, and glare sensation in daylit office-like settings. Correlations between glare sensation assessments and luminance ratios between task area, its immediate surround and far surround were calculated. The results indicate that there are certain definitions of contrast ratio which have better correlations with subjective assessments. The inclusion of this type of glare will enhance the existing glare models for better prediction of glare in a wider set of situations.

To understand how daylight gives shape and life to architectural spaces, whether existing or imagined, requires quantifying its dynamism and energy. Maintaining these details presents a challenge to simulation and analysis methods that flatten data into discrete images or virtual sensor points from a point and time. To address this challenge, this thesis presents a new method for sampling and evaluating simulated daylight. It is intended as a bridge between image-based and sensor-based methods; one that can produce image-level high accuracy directional distribution data with much shorter simulation times that are closer to sensor-based methods. Instead of producing a fixed grid of points, pixels, and sun directions, an iteratively guided sampling approach structured by the discrete wavelet transformation captures the distribution of light incident on a viewpoint with a variable density. By storing the direction vector and effective solid-angle of each sampled ray, the data can be directly evaluated for any luminance-based quantity and view direction. Coupled with daylight coefficients, where the contributions from regions of the sky-dome are recorded rather than associating a value to every possible sky distribution, these methods reduce simulation time at three stages by reducing the number of samples. With fewer samples, it takes less time to render, less time to combine with sky values, and less time to evaluate potential glare sources. Through a series of simulated reference validations, this thesis shows that the proposed method can reproduce the value predicted by a high quality reference simulation in a small fraction of the time. The method achieves higher accuracy results compared to those of existing simulation methods that rely on simplifications. The method is robust across a wide range of daylight conditions and can be tuned to the desired scope of the output. The method can be applied to render a single image in high detail or used to calculate glare metrics in order to evaluate a whole building zone. This method enables a more complete characterization of daylight and visual comfort across an occupied zone; one that is less biased by proxy measurements, representative point selection, or assumptions about glare-causing pathways. Using these methods, we can more reliably understand how daylight will respond to proposed interventions, which should be useful for guiding design, regulatory standards, and improving performance.

Avoiding discomfort glare is one of the critical aspects of maintaining visual comfort, which significantly influences occupants' overall satisfaction with their indoor environment. Discomfort glare prediction models have been developed for various lighting conditions, and their equations commonly use either contrast and/or saturation terms to account for glare caused by excessive luminance contrast or excessive overall brightness, respectively. Daylight Glare Probability (DGP), which includes both terms (hybrid model) and thus accounts for both effects, is one of the more robust ones. However, the predictive performance of discomfort glare models is limited to the luminous conditions and light source types found in the dataset from which they were developed. As daylight glare models like DGP are typically derived from glare evaluations in brightly lit environments, their performance in dimmer conditions, such as those found in deep open-plan workspaces away from the window, could be limited. This thesis, therefore, aims to extend the prediction range of existing discomfort glare models to reliably cover low-light ranges as well. To determine which conditions are most critical to focus on, the luminous ranges covered in previous laboratory studies were compared to those that can be expected in open-plan offices where low-light conditions may occur. The identified range of missing lighting conditions was then used to design and conduct two new user studies in semi-controlled dim daylit conditions to supplement prior discomfort glare datasets. In the first study, participants evaluated four scenes in which the size and luminance of the glare source were varied, and in the second, participants evaluated four scenes in which it was the size and position of the glare source were varied. In parallel, the models that currently perform best in dimmer conditions were identified using an existing dataset of glare evaluations in daylit conditions: contrast-driven models were shown to outperform saturation-driven models in dim conditions, while the more versatile hybrid metrics tended to perform well overall. Hence, the hybrid format was found to be better suited for extending glare models. To create a comprehensive training dataset for this model extension, the data obtained from the two user studies were combined with experimental data from other recent studies containing high-contrast scenarios, namely with the sun disc visible through fabric shadings and low-transmittance glazing. A new best-fit discomfort glare prediction model was then proposed for the broader targeted range of luminous conditions. Based on preliminary performance checks, the new hybrid model appears to fit the participants' glare responses better in low-light conditions than the reference model, DGP, while maintaining a fit equivalent to DGP in brightly lit conditions. The new user studies also revealed an unexpected finding: the summation of multiple glare sources in glare model equations can sometimes result in an over-prediction of discomfort glare. More research will be needed to validate the newly proposed model using a larger test dataset that does not include data points used for any model development. This thesis' findings may help to advance daylight glare prediction in indoor spaces by broadening the range of validity of prediction models to dimmer conditions, thus improving the overall reliability of visual comfort appraisal in the built environment.

In this tutorial the basic usage of raytraverse to complete annual glare simulation tasks is covered. Raytraverse is a software for managing and speeding up the simulation of daylight in building.

Spectrum and correlated colour temperature of light are shown to influence human visual comfort. Previous research conducted with electric light, mainly in the context of vehicular headlamps, have demonstrated that coloured LEDs induce more discomfort glare than white LED and among the coloured LEDs blue ones gave the highest glare perception[1]–[3]. However, there are currently no studies that determine the influence of filtered daylight on discomfort glare in context of daylit indoor spaces which can prove valuable for building façade industry. The spectral power distribution of the daylight inside a space can vary depending on the glazing spectrum. With the current trend of tinted glazing such as electrochromic (EC) glazing and dye-sensitized solar cell glazing that alters the spectrum of daylight, there is a need to extend these results under daylit conditions. To address this gap, we conducted a between subject study investigating the effect of glazing color on occupants’ glare perception under blue-tinted EC glazing (20 participants) and color-neutral glazing systems (55 participants), both widely employed in commercial buildings. We exposed the participants to four visual scenarios with different low glazing transmittances and the sun as the only glare source visible through the glazing. The tests were conducted in a semi-controlled office-like test room with daylight as the only source of light. The glazing’s spectral transmittances were experimentally determined in a dedicated glazing and nanotechnology lab facility. During the exposure time, participants were given a typing task that allowed them to visually adapt to each experimental scenario. Afterwards, participants filled a questionnaire indicating their level of visual comfort. We captured high dynamic range images of each experimental scenario from participant’s eye position to record the scene luminance and calculate various daylight glare metrics. Comparing participant’s responses to glare, we found that through color-neutral glazing of various transmittances, the reported level of discomfort was similar to EC glazing for twice the sun disc’s luminance, thereby indicating that glare was perceived stronger for a blue-colored glare source. This outcome questions whether we measure the luminance and glazing transmittance correctly under tinted glazing scenarios, since the standard way of measuring photometric quantities uses the CIE V2() function for 2-degree standard observer but falls short of explaining the enhanced glare sensitivity under shorter wavelengths. To further delve into this question, we applied the standard CIE V10() sensitivity curve along with earlier proposed luminous efficiency functions for discomfort glare and compared them in terms of their ability to account for differences in the perceived discomfort glare. The results showed that none of these luminous efficiency functions can explain the increased sensitivity for blue-colored glare source that was found, which indicated that its cause should be sought elsewhere. Based on the results, we provide recommendations towards the transmission thresholds for switchable glazing to prevent glare risks when sun is in the field of view. Outcomes of this study can be further implemented to the future development goals for switchable glazing systems and architectural façade design application in achieving visually comfortable spaces. References: [1] Y. Yang, R. M. Luo, and W. Huang, “Assessing glare, Part 3: Glare sources having different colours,” Lighting Research & Technology, vol. 50, no. 4, pp. 596–615, Jun. 2018, doi: 10.1177/1477153516676640. [2] M. Sivak, B. Schoettle, T. Minoda, and M. J. Flannagan, “Short-Wavelength Content of LED Headlamps and Discomfort Glare,” The Journal of the Illuminating Engineering Society, vol. 2, pp. 145–154, 2005, doi: 10.1582/LEUKOS.2005.02.02.006. [3] J. Fekete, C. Sik-Lányi, and J. Schanda, “Spectral discomfort glare sensitivity investigations,” Ophthalmic and Physiological Optics, vol. 30, no. 2, pp. 182–187, Mar. 2010, doi: 10.1111/j.1475-1313.2009.00696.x.

Windows in workplace environment are desirable for their several proven physiological, psychological and economic benefits. Daylight from windows is also responsible for glare which can cause occupants to close the blinds. Glazing properties of the windows play a key role in defining the quality and quantity of the transmitted daylight in a space and therefore controlling glare. With the current trend of colored glazing such blue electrochromic glazing, colored PV panels, dye-sensitized solar cell glazing, it is essential to know the effect of altered spectrum of daylight on glare perception which has not been studied yet. Towards this end, we determine for the first time whether the spectrum of daylight glare source (i.e. the sun) altered by colored glazing influences human perception of glare in workplace scenarios following a psychophysical procedure. We designed a controlled lab study with 50 participants experiencing glare under red, blue, green and grey (color-neutral) colored glazing in an office-like test room with sun behind the glazing as the only glare source. The study was designed as a combination of within-between design where color of glazing was changing within participants and transmittance of glazing was changing between participants. Each participant was exposed to all four colored glazings with similar visible light transmittances resulting in exposure to similar levels of glare metrics values and the color of glazing was the only variable within the tested scenes. Two levels of glazing transmittances (τv = 0.3%, 3%) were tested under all four colors with 25 participants under each transmittance. Results indicate that there is an influence of color on participants perception of glare independent of transmittance. We found that the participants experienced statistically much higher levels of glare under red glazing followed by blue glazing and least discomfort under grey and green glazing. These results indicate a clear effect of color or glare source spectrum on glare perception and calls for an update to glare metrics to include this effect to account for the differences in perception of glare. Results further indicate the inapplicability of photopic luminosity function V () in quantifying luminance for brightly lit saturated colored glare sources.