The authors examined the effect of external shading system on cognitive performance, alertness and visual comfort of visual display terminal (VDT) users under two realistic office lighting settings in this study. Daylight was the source of illumination being considered as the most significant and preferred one. A total of 26 participants performed visual and cognitive demanding tasks as well as providing subjective alertness, performance and visual evaluations in a full-scale mock-up VDT workstation. Two trials (with and without shading system) were executed during one experimental session. Results revealed that the use of a shading system improves the performance of a user on colour-naming task requiring sustained attention, while no differential effects were observed on tasks involving other cognitive skills such as search velocity and vigilance. Within-subject performance differences were more pronounced during morning hours. Higher performance was reported in some cognitive tests when the subjective sensation of visual discomfort was lower.

This study explored the impact of daylight illuminance on cognitive load during visual display terminal use by means of various physiological, performance and subjective measures. Repeated-measures design was adopted to identify the impact of variations in daylight levels that were manipulated through the shading system configurations (shading-on; shading-off). A total of 30 subjects performed visual and cognitive demanding tests. Performance measures were supported by subjective data and eye-related measures during the experimental analysis. Results revealed that the use of a shading system had positive impact on sustained attention. Concerning ocular measures, percentage of eye closure values showed opposite tendencies among vigilance and sustained attention demanding tests. Eye aspect ratio-max and blink duration were significantly correlated with reported glare sensation. In all tests, eye aspect ratio-max was found significantly higher in lower illuminances. Search velocity was significantly correlated with ocular variables in higher illuminances whereas sustained attention showed an opposite trend. This, initially, explains that even slight differences in daylight illuminance might have distinctive effects on the relationship between different groups of assessment variables while measuring cognitive load. Secondly, it proves the significance of carrying out sensitive experiments in terms of both light levels and test characteristics. Practical application: The findings of this study could suggest that a practical application, the use of a shading device, might deliver an efficient solution on such a multifaceted question about the potential effects of luminous environment on the evaluation of cognitive load. Work environments might be considered as cognitively efficient if only the harmony of less mental effort, more satisfaction and less health problems exist, which together ultimately deliver higher work performance. In real-world work environments, application of such shading devices involves advantages not only for avoiding excessive daylight exposure or optimizing energy consumption, but also facilitating cognitive, affective and physiological processes of individuals.

Uncontrolled daylight brings visual and thermal problems that may result in negative interactions with user comfort, productivity, well-being, and human health. Library spaces, in which reading, writing, and computer task activities are performed, need to be well designed in terms of daylight performance to enhance user satisfaction. The focus of this study is to make a performance test of a light shelfreflective louver system to improve the visual performance conditions of a library reading room. First, the instrumental monitoring of existing daylighting conditions was performed. Second, Relux model was prepared to evaluate luminance patterns and illuminance distribution. Third, a new light shelfreflective louver system was proposed based on the insufficiencies of the simulation results. The performance of the new system was found highly satisfactory based on the findings of enhanced luminance patterns and uniformity ratios especially at the points near the windows.