Simulation of daylight availability, visual comfort and view clarity for a novel window system with switchable blinds in classrooms

Abstract

The presence of daylight reflections on blackboards in classrooms can be disruptive to students and negatively impact their visual comfort and learning efficiency. A novel window system with switchable blinds has been specifically designed to balance daylight availability, visual comfort, and adequate window view in classrooms. This study aims to develop a validated simulation method to assess the daylighting performance of the novel window system in these three domains. Radiance-based simulation using bidirectional scattering distribution function (BSDF) data was developed and validated against experimental measurements in a test room. Daylight autonomy (DA) was used as the criterion for daylight availability, while the contrast ratio on the board was used to evaluate the disturbing light reflections on it. The simulation results show that, regardless of the classroom orientation (south/east/west), the novel window system with switchable blinds can: a) successfully meet the LEED requirements for spatial daylight autonomy (sDA) > 55%; b) reduce the low-contrast areas on the blackboard by adaptively switching the blinds, and c) maintain a satisfactory openness of the window with a clear image of the exterior. The studied window system with switchable blinds can provide a sensible balance between daylight availability, visual comfort, and view. The method of rating visual comfort in classrooms using contrast ratio on the blackboard was demonstrated to be feasible and applicable.