On the passive lighting contribution of photoluminescence for innovative window applications for visual comfort

The impact of windows’ properties on buildings’ visual environment and energy performance has been under investigation for a long time. In this context, peculiar materials with photoluminescent properties may be considered for energy-saving purposes. In this work, materials that persistently emit light after being activated by solar and/or artificial radiation are introduced as windows coatings. Their two-fold behavior as diurnal translucent materials and nocturnal light emitters is analyzed by means of a multiscale approach. After the optic and photometric in-lab characterization, the best photoluminescent options are applied to a real environment and monitored according to different boundary conditions, focusing on the photoluminescent gain for indoor lighting. Results prove that a translucent-photoluminescent solution is preferable if compared to an opaque one, despite its lower afterglow intensity. Indeed, a homogeneous daylight diffusion is better perceived for visual comfort, together with a reduced glare probability, while a general sense of orientation is provided by photoluminescence during the evening hours.