Analysis of Circadian Stimulus and Visual Comfort Provided by Window Design in Architecture

Abstract

Light is the major synchronizer of circadian rhythms to the 24-hour solar day. Compared to the visual system, the circadian system requires more light to be activated and is more sensitive to short-wavelength light. Daylighting is an ideal light source for circadian entrainment. Architectural and design features, such as window size and room reflectances impact the amount of circadian stimulus that the patient will receive. DaySim 3.2 simulations were used to determine the percentage of days that occupants would receive a minimum circadian stimulation of 0.50 for at least an hour during the morning. According to a phototransduction model of the human circadian system, a circadian stimulation of 0.50 is equivalent to suppressing the hormone melatonin by about 50%. This circadian stimulus criterion is examined for different window to wall ratios, for two average room reflectances, and for four latitudes. The present paper provides an example of a tool that could be used to assist designers in fenestration and interior design.