Toward a Connected System—Understanding the Contribution of Light from Different Sources on Occupants’ Circadian Rhythms

Wenye Hu,Wendy Davis

doi:10.3390/app11219939

Abstract

Light that enters humans’ eyes and impacts circadian rhythms may come from various sources, including the sun, electric lighting systems, and self-luminous displays. Occupants’ activities strongly impact the light entering their eyes, which is difficult to predict and not yet well understood. This study investigated the circadian contributions of light from different sources in real building environments to better understand the variables that influence the circadian health of occupants. Spectral irradiance distributions at a position equivalent to the front of an eye of a seated occupant in various interior office spaces were collected. Daylight and electric light were measured separately, and light emitted from displays was measured when a variety of different computer tasks was performed. Circadian stimulus (CS) and α-opic irradiance, defined by CIE DIS026/E:2018, were further calculated, and the circadian effects of light from different sources were compared. The results show that daylight has the greatest circadian effect, while electric light in spaces that were predominantly designed with conventional downward lighting has a very limited impact. The circadian effect of light from screens was considerably high. The outcomes suggest that, to optimise the circadian effects of light, connected lighting systems are needed to control light from different sources.

Highlights

Scientific evidence clearly shows that light impacts human circadian rhythms [1,2,3,4,5].Within the lighting industry, there is much enthusiasm for manipulating the spectral output of electric lighting systems to improve the health of building occupants [6]
Studies have been conducted to investigate the circadian effects of daylight and electric lighting, field studies in real architectural spaces to compare the influences of light from different sources are limited
The average circadian stimulus (CS) values in the home offices are all below the threshold (0.1), which suggests that the circadian effect of light is limited in current residential buildings

Summary

Introduction

There is much enthusiasm for manipulating the spectral output of electric lighting systems to improve the health of building occupants [6]. Using light to improve human’s well-being is more complicated in real architectural spaces because light comes from various sources, including daylight, electric light, and selfluminous displays. Studies have been conducted to investigate the circadian effects of daylight and electric lighting, field studies in real architectural spaces to compare the influences of light from different sources are limited. The lack of empirical data makes the design of human-centric lighting and the development of innovative products challenging. This research aims to understand the effect of light from different sources on human circadian rhythms in office settings, based on field measurements. The outcomes of this work may guide the development of innovative human-centric lighting systems

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