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Sunlight is a multisensory phenomenon that can enhance occupant's comfort, health, and connection to the outside environment through its dynamic luminous and thermal attributes. One gap in the existing literature on sunlight exposure is in addressing the visual interest of sunlight patterns and its potential effects on visual comfort. This study employed an experimental procedure where 33 office workers were subjected to three different window and sunlight patterns: fractal pattern, striped pattern, and clear at an office building over three days (one condition per day). Subjective ratings and physical environmental measurements were collected and analyzed to understand differences among the three conditions. Results showed no significant differences in visual comfort or visual interest of sunlight patterns among the three conditions. Desk layout influenced visual interest and view quality ratings. The fractal and striped patterns negatively influenced view quality compared to the clear condition. These results suggest that the shape of window and sunlight patterns might have limited to no impact on visual comfort and interest in offices when workers are preoccupied performing typical office work. [ABSTRACT FROM AUTHOR]

The IESLighting Measurement 83-12 Approved Method: IES Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE)(LM-83) codifies annual climate–based daylighting metrics and performance criteria, yet interpretation and application of the metrics and criteria are not fully substantiated. This article reports “daylit area” drawings prepared in the field by architecture students and compares these drawings to corresponding point-in-time and annual daylighting simulations. The point-in-time simulations without blinds showed less discrepancy between student daylit area evaluations than did annual simulations with blinds operated per LM-83. The daylit area drawings and point-in-time simulations together suggest a horizontal illuminance of 100 lx differentiating between non-daylit and partially daylit areas and 250 lx differentiating between partially and fully daylit areas. For 18 annual simulations that employed the LM-83 protocol, half were characterized similar to the field assessments. The other half consistently underpredicted daylight ratings; students found the spaces to be fully or partially daylit when the annual simulation predicted the spaces to be non-daylit. This study suggests that the spatial daylight autonomy (sDA) and ASE criteria in LM-83 may warrant refinement. [ABSTRACT FROM AUTHOR]

This paper documents a field study that collected visual comfort feedback and High Dynamic Range (HDR) luminance maps to test the validity of laboratory-derived metrics in field settings. This study included 13 subjects for 149 daylighting evaluations. Similar to previous laboratory-based research, simple luminance-based metrics outperformed complex glare indicators in their predictive ability in this pilot field study. Also similar to lab studies, metrics derived using luminance data within the horizontal 40° band of human vision and a mask of just the window represented the majority of the top 20 squared correlation coefficients, considering all questionnaire items. While standard deviation of window luminance, a highly predictive metric derived in a laboratory setting, did not maintain similar predictive ability in these field studies, the field study supported previous laboratory findings that this metric may be useful in discerning visual discomfort in spaces that are very dim. Two new metrics, the ratio of the 98th percentile to mean window luminance and the coefficient of variation (COV) of luminance in the horizontal 40° band, yielded the strongest squared coefficients in field studies ( adj r 2 = 0.35 and adj r 2 = 0.32 respectively). The COV 40° band was more stable across multiple positions within a scene than other luminance-based methods. These findings suggest that some metrics are better suited for use within a single room over time (for purposes of dynamic daylighting scene control), whereas other metrics are better suited for evaluation between spaces and from alternate positions within a room (for purposes of design guidance). [ABSTRACT FROM AUTHOR]

A new suite of visual comfort metrics is proposed and evaluated for their ability to explain the variability in subjective human responses in a mock private office environment with daylight. Participants (n= 48) rated visual comfort and preference factors, including 1488 discreet appraisals, and these subjective results were correlated against more than 2000 unique luminance-based metrics that were captured using high dynamic range photography techniques. Importantly, luminance-based metrics were more capable than illuminance-based metrics for fitting the range of human subjective responses to data from visual preference questionnaire items. No metrics based upon the entire scene ranked in the top 20 squared correlation coefficients, nor did any based upon illuminance or irradiance data, nor did any of the studied glare indices, luminance ratios, or contrast ratios. The standard deviation of window luminance was the metric that best fit human subjective responses to visual preference on seven of 12 questionnaire items (withr2= 0.43). Luminance metrics calculated using the horizontal 40° band (a scene-independent mask) and the window area (a scene-dependent mask) represented the majority of the top 20 squared correlation coefficients for almost all subjective visual preference questionnaire items. The strongest multiple regression model was for the semantic differential rating (too dim–too bright) of the window wall (adjR2= 0.49) and was built upon three variables; standard deviation of window luminance, the 50th percentile luminance value from the lower view window, and mean luminance of the 40° horizontal band. [ABSTRACT FROM PUBLISHER]

Abstract: There is no comprehensive consensus about the way people operate blinds or the motivating factors that influence their decisions. However, there is a substantial body of research, encompassing data from more than 50 buildings worldwide, that offers guidance. Patterns of blind use can affect the energy consumption of buildings substantially and therefore energy and daylighting simulations that do not account properly for these blind use patterns will have greater error. An outline for a new more nuanced model for simulation-based blind control is offered. Specifically, this paper reviews the energy implications of blind use, blind occlusion and rate of change from field studies, specific quantitative measures influencing user blind control, investigations into user acceptance of automated blind control, and finally conclusions and knowledge gaps are summarized and suggested next steps for research are provided. Addressing these gaps is critical for the continued progress of the energy efficiency movement. [Copyright &y& Elsevier]

Daylight has the potential to positively impact occupants and reduce energy consumption in buildings if utilized correctly (). However, unintended negative outcomes can arise from unsuccessful daylighting schemes. Common issues, such as glare and heat gain, are important architectural considerations in design of the building envelope, but less studied are corresponding interior design considerations ( such as furniture layout and access to controls) and associated occupant interactions and appraisals. The purpose of the current study is to expose some of the key issues related to the occupant use of daylight and daylight control in perimeter offices, to discuss the contributing design process factors, and to suggest possible improvements to the design process including an increased role for interior designers. The research methodology followed a case study approach and included post-occupancy evaluation (POE) questionnaires, interviews, and observations of a single higher education building with intentionally daylit perimeter offices. We discovered that the building in question was passed between three separate design teams throughout the design process, which may have contributed to the lack of integration between the architectural daylight design and the interior furniture and daylighting control fit-out. More than 50% of total respondents ( n = 35) reported obstructed blind controls due to poor furniture design and layout. Of these, nearly 60% of occupants modified their office environment to gain access to blind controls. Ultimately, findings of this study demonstrate the importance of an integrated, multidisciplinary approach to daylighting design, one that considers both the specific building context and the human response. [ABSTRACT FROM AUTHOR]

New research in daylighting metrics and developments in validated digital High Dynamic Range (HDR) photography techniques suggest that luminance based lighting controls have the potential to provide occupant satisfaction and energy saving improvements over traditional illuminance based lighting controls. This paper studies occupant preference and acceptance of patterns of luminance using HDR imaging and a repeated measures design methodology in a daylit office environment. Three existing luminance threshold analysis methods [method1: predetermined absolute luminance threshold (for example, 2000 cd/m²), method2: scene based mean luminance threshold, and method3: task based mean luminance threshold] were studied along with additional candidate metrics for their ability to explain luminance variability of 18 participant assessments of 'preferred' and 'just disturbing' scenes under daylighting conditions. Per-pixel luminance data from each scene were used to calculate Daylighting Glare Probability (DGP), Daylight Glare Index (DGI), and other candidate metrics using these three luminance threshold analysis methods. luminOf the established methods, the most consistent and effective metrics to explain variability in subjective responses were found to be; mean luminance of the task (using method3; adjr² = 0.59), mean luminance of the entire scene (using method2; adjr² = 0.44), and DGP using 2000 cd/m²as a glare source identifier (using method1; adjr²= 0.41). Of the 150 candidate metrics tested, the most effective was the 'mean luminance of the glare sources', where the glare sources were identified as 7* the mean luminance of the task position (adjr²= 0.64). Furthermore, DGP consistently performed better than DGI, confirming previous findings. 'Preferred' scenes never had more than ~10 percent of the field of view (FOV) that exceeded 2000 cd/m2. Standard deviation of the entire scene luminance also proved to be a good predictor of satisfaction with general visual appearance. [ABSTRACT FROM AUTHOR]