Analysis of circadian stimulus allowed by daylighting in hospital rooms

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. Without access to daylight, or electric lighting providing comparable amount, spectrum, distribution, duration, and timing, human health and wellbeing may be compromised. This may be particularly true for those confined indoors, such as patients in hospitals and residents in eldercare facilities. Architectural and design features, including window size, surface reflectances and furniture placement, impact circadian stimulus levels. The present paper details results of simulations used to determine percentage of days that patients would receive a minimum level of circadian stimulation as a function of different window-to-façade ratios, surface reflectances, and latitudes.