Atrium Design and the Science of Daylighting: A Comparative Field Study

Abstract

Scientific and analytical advances in lighting design metrics have created a perspective that empirically defines measurable parameters of daylight. These have narrowly focused on illuminance-based metrics of light and energy efficiency of high-performance buildings and disregarded the qualitative and health-effective dimensions of daylight. Design strategies implemented should not only meet green building standards and certification guidelines, but also consider human physiological and psychological responses. The intent of this study is to investigate the effectiveness of the design approach of atriums in two LEED educational buildings with regards to building performance, chronobiological benchmarks, and occupant’s behavior. To assess visual comfort and discomfort, light illuminance and spectral power distribution measurements were taken inside both atriums to analyze the spaces throughout a typical equinox day, and at different days for varying sky conditions. The results from this visual environment analysis were then translated to assess health effective light received with the use of the circadian stimulus (CS) and equivalent melanopic lux (EML) metrics. Behavioral logs and surveys were also documented to help establish any patterns that could draw attention to human responses which could identify mediating factors in the indoor environment. Results indicate that illuminance level measurements taken on horizontal planes tend to be greater than those in vertical planes facing different directions. This addresses designers’ misconception that meeting a spatial Daylighting Autonomy at the 300 lux benchmark (sDA₃₀₀) on the horizontal working plane is sufficient. It is also noted that meeting the sDA₃₀₀ benchmark is not a strong indicator of maintaining 0.3 circadian stimulus or 250 EML benchmark. Both circadian stimulus and equivalent melanopic lux biological benchmarks appear to be more difficult to meet than the visual task illuminance level benchmark requirements. This chapter highlights how human responses to the design of the luminous environment fit in the overarching scheme of daylighting design parameters and metrics. It emphasizes lesser known potential health effective light metrics adopted in the field for increased applications.