Energy impact of human health and wellness lighting recommendations for office and classroom applications

The goal of this investigation was to evaluate potential energy impacts of circadian lighting design recommendations that are gaining attention in a variety of common applications such as offices and classrooms. The renewed focus on health along with advances in solid-state lighting technology capabilities has underscored that there is still much to learn regarding the relationship between light and human physiology. The energy implications of designing to address these possible physiological effects are not yet fully understood. Beyond the fact that the basic metric of luminous efficacy (lumens per watt) does not cover these other effects, the emerging science seems to indicate that addressing a holistic view of the human needs in most applications may mean a need for increased light and associated energy use by electric lighting systems. Two applications, an open office and a classroom, were simulated and lumen output, spectral characteristics, surface reflectance distribution, and desk orientation were varied to explore the magnitude of potential effects. Meeting current Illuminating Engineering Society (IES) illuminance recommendations did not satisfy existing equivalent melanopic lux and circadian stimulus recommendations for any of the office and classroom simulations. In some cases, satisfying circadian metric recommendations required an average illuminance that was more than double the IES recommendations, which may negatively impact lighting quality. Using results from 45 unique simulation conditions, it was estimated that lighting energy use may increase between 10% and 100% because of increased luminaire light levels used to meet circadian lighting design recommendations listed in current building standards such as WELL v2 Q2 2019, UL Design Guideline 24480, and CHPS Core Criteria 3.0.