A Critical Literature Review of Spatio-temporal Simulation Methods for Daylight Glare Assessment

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

HDR Images for Glare Evaluation: Comparison Between DSLR Cameras, an Absolute Calibrated Luminance Camera and a Spot Luminance Meter

User calibrated digital single-lens reflex (DSLR) cameras are being used in visual comfort and especially for glare evaluations as affordable alternatives to high-end luminance cameras calibrated by the manufacturer itself. While the typical way for a user calibrated camera is the application of an automatic calibration algorithm, manufacturers, on the other hand, tend to rely on a calibration process for their cameras based on measurements performed for each exposure setting (absolute calibration). This paper investigates the accuracy of luminance maps derived from HDR images captured with auto-calibrated DSLR cameras. More specifically, the aim of this study is to compare the luminance values obtained with an auto-calibrated DSLR camera for different light scenarios on one hand to a commercially available camera (that benefited from an absolute calibration) and on the other hand to a handheld luminance meter, considered as the reference. It was found that there are only small differences when luminance values estimated with auto-calibrated DSLR cameras are compared with those obtained for the commercially calibrated camera for low to mid-range luminance values (50 – 5000 cd/m 2 ). However, for higher luminance values (>5000 cd/m 2 ), HDR images from the auto-calibrated camera show differences of up to 20 % when compared to the manufacturer calibrated camera, which could be problematic for glare investigations. More studies specifically focusing on high luminances are thus needed, so as to determine more conclusively whether certain limitations should apply to the use of automatically calibrated DSLR cameras for glare evaluations

User assessment of fabric shading devices with a low openness factor

Providing adequate glare protection and a view to the outside through fabric shading devices is challenging because these two objectives require conflicting material properties for a fully lowered shading. In a semi-controlled office-like experiment involving 32 participants, we investigated four types of neutrally-colored fabrics (charcoal and gray) with Openness Factors (OF) smaller than 7% focussing on view clarity, discomfort glare with the sun in the field of view, and participants\u27 behavior when it comes to blind control. The results show that fabrics with OF6% resulted in lower glare protection but higher quality of view out. Our results show inconsistencies with the EN14501 blind classifications for glare and visual contact (i.e., view clarity), but acceptable agreement with the view clarity index, especially for the fabrics with the highest light transmittance. During the final session, three quarters of participants raised the blinds to allow an average of 10° view to the outside, reporting as primary motivations the wish for more light and view out. Despite the relatively small rise of the fabric (15% of the total shade), daylight levels and view out were significantly improved, suggesting that operable blinds should not be controlled nor described according to the "all-or-nothing" approach. The change in fabric height did not compromise glare perception. These results suggest that if the control of shading height is effectively provided to occupants, then the fabric material could be selected primarily based on glare requirements

Contrast Glare and visual comfort in response to daylight

There are uncertainties in the current daylight glare prediction models as they do not accurately predict the glare sensation that people experience. The objective of this research project is to investigate daylight glare stemming from contrast between task area and its immediate surroundings. In order to control for bias, several of the main factors that are suspected of influencing individuals’ glare ratings will also be investigated, among others self-reported glare sensitivity, gaze direction and eye contrast sensitivity. The expected research outcome is an improvement of the current daylight glare prediction models

The Effect of Coloured Glazing on Thermal, Visual and Overall Comfort Evaluation

Within the scope of a broader research project about visual and thermal interaction effects on human comfort and perception, the aim of this paper is to study the variation of thermal, visual and overall comfort votes of people exposed to blue and orange glazing. The study, conducted in a controlled test room and involving a total of 75 participants, is repeated at three temperature levels to investigate whether variations in comfort votes are affected by the thermal environment. Results show that participants changed their comfort votes for both thermal and overall comfort, beside the expected visual comfort, due to changes in glazing colour. Larger variations in thermal and overall comfort votes are observed in the close-to-comfortable temperature range (22 °C). Temperature-related effects can be seen for visual and thermal comfort evaluations. Overall comfort shows a positive correlation with both visual and thermal comfort

Adaptive visual and thermal comfort

Increasing efforts are devoted to enhance and optimize the environmental comfort in buildings, as this aspect plays a major role in the affection of health, performance and general well-being of people. Indoor air quality, acoustic ambience, light and thermal conditions have been proved to be fundamental factors for the indoor environmental quality. Engineers must be aware of the effects of the interactions between these factors on the indoor comfort as people react simultaneously to diverse stimuli belonging to different sensorial fields and adapting their behaviors according to the associated conditions. Being able to know how these interactions influence the users’ comfort can lead to marked energy savings and positive influence on users’ productivity. Many studies have been conducted on the influence of each component on the overall comfort, but only few studies are available investigating the interaction between different comfort variables of different disciplines. This research focuses on the interaction between visual and thermal comfort for building users in school environments, looking at the impact of different perceptive conditions on the productivity of the users and overall comfort. In particular, it analyzes the effect of visual variables on the perceived thermal comfort and of thermal variables on the perceived visual comfort, beside the mutual interaction of visual and thermal variables on the overall comfort appraisal. The study is based on fundamental concepts belonging to different branches of knowledge, ranging from engineering to psychology and physiology for the considered purpose. These disciplines come together in search for objective interactions between different comforts by means of experiments in realistic climate chamber or controlled field studies. The goal of this study is to propose new guidelines for informing building designers on the interaction between visual and thermal variables and their influence on human comfort and productivity in the built environment. The results of this study will ultimately foster the development of control systems with the aim to achieve energy savings, increase user satisfaction as well as boost productivity