Supporting visual and non-visual lighting design without increasing discomfort glare or lighting power density

With the growing interest in designing circadian-effective lighting, it is becoming increasingly important to determine how different lighting designs aimed at supporting circadian entrainment might also affect visual performance, preference, discomfort glare and lighting power density (LPD). These outcome measures were simultaneously examined in a controlled setting at night. Four ceiling lighting configurations, using combinations of direct and indirect lighting, were implemented along with one design that utilised local lighting. Every design delivered the same high level of circadian-effective lighting to participants. Saliva samples were obtained to measure nocturnal melatonin suppression. Two visual performance computer tasks together with subjective assessments of sleepiness, discomfort glare and preference were administered to participants. LPDs were determined. None of the lighting configurations created unacceptable levels of discomfort glare, and only one was above the required maximum allowable LPD. Lighting configuration had no differential effect on nocturnal melatonin suppression, visual performance and sleepiness. While the results show that a wide range of lighting approaches can meet visual, non-visual and energy objectives, the majority of participants preferred the local lighting over the ceiling-mounted lighting.