Built environment, where humans spend over 90% of their lives, has profound effects on physiological and psychological health. Daylight as an environmental nutrient, is a primary regulator of the human circadian system, influencing sleep, mood and cognitive functions. However, architects have struggled to balance the dual roles of daylighting: a) providing sufficient illumination for visual tasks while b) supporting non-visual biological processes. This study investigates the trade-off between strategies to maximize circadian-effective light and the risk of visual discomfort from glare and over-illumination. To address this conflict, the authors employ a simulation-based framework to evaluate 25 architecturally representative glazing systems. Using 81-channel spectral analysis, each glazing type is assessed under clear and overcast skies across varied orientations and interior positions. Performance is quantified using melanopic equivalent daylight illuminance (EML), daylight glare probability (DGP), and useful daylight illuminance (UDI). The results demonstrate a strong conflict between maximizing EML and minimizing DGP under direct sunlight, revealing a non-linear performance landscape. The findings confirm that any static glazing selection represents an inherent compromise, highlighting the necessity of dynamic, spectrally tunable façade technologies to support circadian health in architecture.
Abedi et al. (2025) studied this question.