A Combined Method for an Exhaustive Investigation of the Anidolic Ceiling Effect on Improving Indoor Office Daylight Quality: an Approach Based on HDR Photography and Subjective Evaluations

Lighting quality in office environments is a broad concept that must be taken into account in the design stage to deliver comfortable spaces to reduce workers' stress. Indeed, daylight should be sufficient to perform visual tasks while avoiding excessive brightness, high contrast, or intense sunlight reflections that can cause discomfort glare. This research aims to test the Anidolic Integrated Ceiling (AIC) performance in creating a visually comfortable space by reducing the probability of glare. A combined method was adopted for investigating the influence of the building orientation and the workers' view directions in the different moments of the day in the winter season. Data collection was performed in an experimental environment, i.e., a physical scale model of 1:4 under real sky conditions. Three variables were: (i) the viewer's positions (parallel and face to the window), (ii) the façade orientation, (iii) the time of the day (morning and afternoon). To investigate the correlation between the simulated environment and the subjective comfort, we collected the following data in parallel: illuminance level, Daylight Glare Probability Index (DGIP), Luminance Contrast Ratios (LCR) for assessing the daylighting environments, and people reactions to the lighting setting to evaluate the perceived discomfort glare. The findings indicate that the Anidolic system's performance differs according to the occupant's orientation and herhis visual direction. The performance of the north façade of the case study application in Biskra, Algeria, was the best one. Indeed, the AIC system allows a harmonious luminance distribution without creating discomfort glare. Glare assessment shows that glare is perceived imperceptible in the lateral view (less than 0.30) and varies between imperceptible and perceptible in the parallel view (LCR values between 1:1 and 1:29). The questionnaire results show that the subjects were more satisfied with the luminous atmosphere of the lateral view than the parallel view where people more likely perceived discomfort. The statistical analysis shows that participants' perceptions of contrast and sensitivity to glare have a strong relationship with DGIP and LCR (0.000) and no correlation with illuminance and LCR.