A pilot experiment on a method for evaluating acceptability of a daylit luminous environment (original) (raw)
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Indoor and Built Environment, 2013
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Energies, 2014
The combined effects of color temperature and illuminance in a small office on visual response and mood under various lighting conditions were examined in this study. Visual annoyance tests were conducted using a sample of 20 subjects in a full-scale mock-up test space. Computer and paper-based reading tasks were conducted for 500 lx and 750 lx illuminance levels under 3,000 K, 4,000 K and 6,500 K conditions. Two hypotheses were considered for the test in this study. The primary hypothesis was that visual perception is affected by the color temperatures of light sources. The secondary hypothesis was that better moods, such as relaxed and cozy feelings, are associated with low color temperatures given equal illuminance levels. The visual environment under the 3,000 K condition was characterized by glare and brightness, resulting in visual discomfort when target illuminance was higher than 500 lx. Occupants preferred 500 lx under the 6,500 K condition, and 500 lx and 750 lx under the 4,000 K condition, reporting better visual satisfaction when performing office tasks. Prediction models for visual comfort suggest that the less that subjects are visually bothered by light during tasks, the more visual comfort they feel. User satisfaction with light source color is critical for the prediction of visual comfort under different lighting conditions. Visual comfort was the most influential factor on mood. Lower color temperature was associated with better mood at lower illuminance levels, while higher color temperature was preferred at higher illuminance levels.
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Civil Engineering and Architecture, 2020
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Proceedings of International Conference CISBAT 2015 Future Buildings and Districts Sustainability from Nano to Urban Scale, 2015
Light entering the human eye does not only enable the performance of visual tasks, but also influences the health and well-being of humans via non-visual effects. A substantial amount of people in the Western society spends the majority of their work time indoors. Welldesigned lighting positively impacts the visual comfort and well-being of people working in offices. Current standards for office lighting design are solely based on enabling the visual tasks via recommendations for photometric quantities such as the maintained illuminance on the task and surrounding areas and/or the glare limitation. The luminous radiation that contributes to the health related non-visual effects is not addressed in these recommendations at all. It is therefore essential to include the impact of effective luminous radiation in the lighting design process. This paper discusses the necessary distinction between photometric quantities on one side and effective luminous radiation on the other side. It investigates the effect of design parameters such as 'window size', 'exterior ground plane color and luminous reflectance' on the visual and non-visual effects for different view directions. Simulations have been conducted for the IEA Task 27 reference office using the light software tool Radiance The findings show reverse influence of the exterior ground plane color and luminous reflectance on the visual and non-visual effects of light. While the exterior ground plane luminous reflectance plays an important role on the visual evaluations, its color is the most influential design parameter for the non-visual evaluations. For the optimal health related nonvisual effects of light, findings suggest using bluish exterior ground plane and placing the work plane facing the window.
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This paper presents an overview of peer-reviewed investigations of subjective issues linked to the use of daylighting in office buildings, particularly studies of preferred physical and luminous conditions in daylit office environments, and studies of occupant satisfaction and acceptance of electric lighting and window shading controls. The literature shows a consistent strong preference for daylight and a wide distribution between individuals in relation to the preferred illuminance levels in daylit offices. Existing knowledge about how people respond to daylight-linked lighting and shading controls in the workplace is very limited; therefore, this paper presents a summary of knowledge gaps in the field of daylighting and its interaction with the occupants. The resulting key directions for future research highlight issues for which a better understanding is required for the development of lighting and window shading control systems that are both energy efficient and suitable for the office occupants. Crown
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A new concept of long term visual comfort is introduced to describe the long-term visual impression of space occupants. This concept, in contrast to instantaneous assessment of visual comfort, aims to describe an overall rating of visual quality. A paired study consisting of occupant surveys and detailed 6-minute timestep comfort simulations was performed for the studio spaces of Gund Hall (Cambridge, MA, USA), which is occupied by over 500 students. Occupants reported four primary ways of experiencing visual discomfort: discomfort glare, insufficient monitor contrast, direct visibility of the sun and direct sunlight on the workplane. Survey results were located spatially and in terms of orientation within Gund Hall, and the simulation model was calibrated based on furniture layout, measured material reflectances and local measured weather data. The results of the study illustrate that it is possible to use current simulation-based visual comfort predictions to predict occupants' long-term visual comfort assessments in a complex daylit space. Between 53.7% and 70.1% percent of polled occupants' evaluations were correctly identified. Through a spatial and temporal presentation of the simulation data, this new methodology can be used as feedback during the process of designing daylit spaces, avoiding visual discomfort and increasing satisfaction with the built environment.