Light as a circadian stimulus for architectural lighting

Consideration is being given to the adoption of a new metric characterizing light as it affects the human circadian system. Much has been learned over the past couple of decades about light as a stimulus for circadian system regulation, so it is appropriate that these discussions take place. The present paper develops an argument for adopting circadian stimulus as a metric for quantifying light in architectural spaces. The circadian stimulus metric (a) was developed from several lines of biophysical research, including those from basic retinal neurophysiology; (b) has been validated in several controlled experiments; and (c) has been used successfully in a number of real-world applications. Any discussions of new metrics should take each of these foundational points into consideration.