Towards a Dynamic Daylight Understanding

Daylighting is still the most energy efficient lighting strategy, but filtering sunlight might conflict with maximization of solar gains in winter or reducing solar heat gain in summer. In passive solar homes occupants ideally balance visual and thermal comfort. This study explores the relationship of daylight and thermal comfort in a passive solar home using an extended case study method. The resulting daylight measurements reveal a significant tolerance for fluctuations in natural illumination, lower than both high and low thresholds used by emerging dynamic daylight metrics such as IESNA Lighting Handbook, Useful Daylight Illuminnance, and CIBSE lighting recommendations. Minimal evidence of electrical lighting use revealed that passive solar occupants have learned to modify the house to receive sufficient daylight while maintaining a comfortable thermal environment. As a result, a preliminary dynamic visual comfort zone is identified, which presents the notion of a metric that includes occupant illumination control.