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A Bidirectional Scattering Distribution Function (BSDF) describes how light from each incident direction is scattered (reflected and transmitted) by a simple or composite surface, such as a window shade. Compact, tabular BSDFs may be derived via interpolation, discretization and/or compression from goniophotometer measurements. These data-driven BSDFs can represent any measurable distribution to the limits of their tabulated resolution, making them more general than parametric or analytical BSDFs, which are restricted to a particular class of materials. However, tabulated BSDFs present a trade-off between higher sampling loads versus lower directional accuracy during simulation. Low-resolution BSDFs (e.g., Klems basis) may be adequate for calculating solar heat gains but fall short when applied to daylight glare predictions. The tensor-tree representation moderates this trade-off using a variable-resolution basis, providing detail where needed at an acceptable cost. Independently, a peak extraction algorithm isolates direct transmission from any tabular BSDF, enabling high-resolution beam radiation and glare analysis through transmitting systems with a “vision” component. Our data-driven BSDF methods were validated with a pilot study of a fabric shade installed in an outdoor, full-scale office testbed. Comparisons between measurement and simulation were made for vertical illuminance, specular and near-specular transmission, and daylight glare probability. Models based on high resolution BSDF measurements yielded superior results when accounting for anisotropy compared to isotropic models. Models with higher resolution produced more accurate source luminance data than low-resolution models. Further validation work is needed to better characterize generality of observed trends from this pilot study.

Micro-cameras such as the ‘vision-in-package’ (VIP) can be used as a wearable for user-centric glare estimations. Yet, there is a lack of methodologies to use such head-mounted device and their outputs to obtain reliable glare evaluations. This paper focuses proposes a methodology for dynamic glare evaluation based on wearable micro-cameras. The methodology involves a novel image rotation algorithm and pixel overflow correction based the solar disk luminance measured using an HDR camera. We tested the methodology during an experiment where 21 participants were exposed to direct sunlight in an office-like set-up in Lausanne, Switzerland. For our dataset, the pixel overflow correction avoids an underestimation of the DGP metric in 94.8% of the cases. These corrections appear crucial for the correct estimation of glare using wearable VIP cameras.

Recently, there have been multiple proposals for faster methods to calculate glare metrics, daylight glare probability (DGP) in particular. This is driven simultaneously by the lengthy times required to simulate DGP with a conventional image-based approach and accumulating evidence from subjective glare evaluation experiments showing that accounting for both the saturation and contrast in a view improves the accuracy of a glare prediction. While some of these methods have been presented with their own validations, comparisons of accuracy across methods are limited by the differences in tested scenarios and resulting distributions of daylight conditions. This study compares six point-based methods and two zonal estimations for quickly calculating hourly DGP values from three viewpoints with different relationships to the window across a range of scenarios. These include scenarios with direct and semi-specular transmission and others with specular and semi-specular reflection. We find that while some of these fast methods closely align with results from a reference simulation, others introduce large and consequential errors.

A recent study on the glare protection performance of electrochromic (EC) glazing showed that visible transmittance levels lower than 0.6% are necessary to achieve comfortable situations for sun positions, that were close to the central field of view. However, the question that arises is how often such situations occur throughout the year and how the glare protection performance of EC systems is for typical office situations for different climates and orientations. This study aims to quantify the annual performance for such configurations by applying improved simulation methods to conduct annual glare simulations and comparing them to the EN17037 classifications. The enhancement of the simulation method compared to existing methods was necessary to correctly consider the blurring effect in the lens of the eye – neglecting this would lead to an overestimation of glare. We found that for mid and north European climates the extreme situations do not occur such often, so that the ECglazing systems being able to switch to transmittance levels of 1% can mitigate glare throughout the year reasonably well for typical office situations and reaches typically the highest glare protection category according to EN17037 for a viewing direction, that is parallel to the facade. For more sunny climates such as Rome, slightly lower transmittance levels (around 0.5%) would be necessary to achieve a similar glare protection level. The study also revealed that tables E.7 and E.8 of EN17037 with pre-calculated 95-percentile Daylight Glare Probability (DGP) values should be re-calculated.

The size of window openings is widely acknowledged as an important factor in our spatial perception. However, little is known about how the perception and preference of windows changes between countries, leaving a gap of knowledge regarding the applicability of research findings across latitudes. This article presents the outcomes of a study investigating regional differences in the perception of spaces with varying window size (small, medium, and large), space size (small and large), spatial context (working and social), and sky type (overcast and two types of clear sky). As the regional differences were the main studied factor, the study was performed in Norway, Switzerland, and Greece, representing northern, central, and southern European latitudes, respectively, and used virtual reality as a means to replicate the same experiment in different locations. In total, 406 participants evaluated eight spatial attributes using an 11-point Likert-type scale. Results indicated that regional differences could be observed in the participants' responses, with significant differences in how pleasant and calm the space was perceived, found not only between participants in Greece and Norway in all the studied window sizes, but also between Greece and Switzerland for the medium and large windows, indicating that even small variations in latitude within Europe can affect the spatial perception. The findings of this study reveal that spaces with specific fenestration characteristics might not induce the same response across different latitudes in Europe, and thus, have important implications for daylighting and architectural design, which would motivate the use of region-specific parameters. [ABSTRACT FROM AUTHOR]

Daylight provision to the indoor space is affected by different building elements that cannot be fully controlled by the users, such as the window size of a space. The dimensions of the fenestration not only affect the lighting levels, but they also affect how the space is perceived by its users. The present study examines three different window sizes via virtual reality, to study how they affect the perception of both a small and a large space at high latitudes. Additionally, two context scenarios (socializing and working), as well as three different sky types (overcast sky and clear skies with either high or low sun angle) were evaluated. The experimental study applied a mixed design with within-subjects and between-subjects factors. A total of 150 participants evaluated the scenes using a Likert-type scale to rate eight different subjective attributes. The statistical results showed that both window size and space type significantly affect the participants' spatial perception, as well as their satisfaction with the amount of outside view. Larger windows led to more positively evaluated spaces for all studied attributes. Moreover, a significant interaction was found between window size and type of space for the satisfaction with the amount of view in the space, indicating that the window size was dependent on the type of space in which the windows are located. Specifically, the window sizes were rated higher in the small space than in the large space for the evaluation of amount of view. The findings show that window size affects how people perceive a space, and additionally, that other spatial features, such as space type, affect window size preferences. [ABSTRACT FROM AUTHOR]

Objective: Temperature-color interaction effects on subjective perception and physiological responses are investigated using a novel hybrid experimental method combining thermal and visual stimuli from real and virtual reality (VR) environments, respectively.Background: Despite potential building design applications, studies combining temperature with daylight transmitted through colored glazing are limited due to hard-to-control light conditions. VR is identified as a promising experimental tool for such investigations that overcomes the limitations of experiments using daylight.Method: Fifty-seven people participated in an experiment combining three colored glazing (orange/blue/neutral) and two temperatures (24°C/29°C). Exposed to one color-temperature combination, participants evaluated their thermal, visual, and overall perception, whereas their physiological responses (heart rate, skin conductance, and skin temperature) were continuously measured.Results: Daylight color significantly affected thermal perception, whereas no significant effects of temperature on visual perception were found. Acceptability of the workspace was affected by both color and temperature. Cross-modal effects from either daylight color or temperature levels on physiological responses were not observed.Conclusion: In the VR setting, the orange daylight led to warmer thermal perception in (close-to-) comfortable temperatures, resulting in a color-induced thermal perception and indicating that orange glazing should be used with caution in a slightly warm environment.Application: Findings can be applied to the design of buildings using new glazing technologies with saturated colors, such as transparent photovoltaics. Despite some limitations, the hybrid environment is suggested as a promising experimental tool for future studies on indoor factor interactions. [ABSTRACT FROM AUTHOR]

This paper presents the combined effect of indoor temperature (19 °C, 22 °C, and 26 °C) and colored glazing (blue, orange, and neutral) on visual perception of daylight. Experiments were performed in an office-like test room, in which 75 participants were fully immersed under visual and thermal stimuli. Findings are discussed in terms of cross-modal effects of indoor temperature on visual perception, as well as of unimodal effects of glazing color on visual perception, investigated in terms of color of light and visual environment evaluations. Results show the presence of cross-modal effects of indoor temperature on visual perception of both the visual environment and the color of light. Indoor temperature affected the visual environment evaluation as, first, brightness comfort resulted higher at lower temperatures, and second, the light was associated to warmth adjectives more often at higher temperatures. On the other hand, indoor temperature influenced the color of light evaluation as, only at lower temperatures, daylight tinted by the blue glazing was considered less pleasant and less comfortable, and was chosen less often over the daylight tinted by the orange glazing. In terms of unimodal effect of colored glazing on visual perception, results indicate that the neutral glazing was always preferred over the two colored ones, probably due to the use of saturated colors. The orange glazing, however, was associated with the most relaxing and warmest daylight. These findings have important implications regarding the use of glazing with saturated colors in buildings and expand our understanding of temperature–color interaction – so far investigated only with electric light – to daylight evaluations. [ABSTRACT FROM AUTHOR]