Daylight Exposure and Circadian Efficiency in Office Rooms Equipped with Anidolic Daylighting Systems

Anidolic Daylighting Systems (ADS) typically reduce the daylight flux reaching an office room‟s window section and increase it in the rear of the room. They offer interesting possibilities for the combination of comfortable daylighting and highly energy-efficient office lighting designs. The objective of this study was to get an insight into typical ocular daylight exposures in office rooms equipped with ADS and to compare them to an artificial blue-enriched light source. Results from a recent study by Viola et al. [9] demonstrated that the use of the same light source positively influenced subjective wellbeing and sleep quality in office workers. We recorded daytime irradiance values for several weeks from April-May 2009 in an experimental office setup in our laboratory using a portable digital spectroradiometer. The artificial light sources were measured during the night. With respect to more circadian aspects of day- and artificial lighting designs we finally corrected the measured irradiances with a c(λ)-curve. Our results showed to which extent external sky conditions influenced light exposure of office workers in an ADS-equipped office room for different sky types. The considered ADS was able to supply natural blue light irradiance levels during large parts of days with intermediate and clear skies, which were much higher than those created by our artificial lighting installation based on two blue-enriched fluorescent lamps. The same was true for weighted circadian irradiance values Eec. We conclude that for the tested ADS-equipped office room, complementary artificial lighting with blue-enriched polychromatic fluorescent tubes might be useful on days with predominantly overcast skies and before 09:00 and after 16:30 on all days.