IES 2021 Annual Conference

LED technology for general lighting has advanced greatly over the past many years, providing quality illumination at much lower energy cost than traditional systems. However, there is a growing concern that some of the energy savings achieved by LEDs may be offset by emerging lighting requirements for circadian health that could require higher light levels and energy usage. This project sought to quantify the energy impacts of meeting circadian criteria with non-tunable LED troffers as well as with tunable white LED troffers and pendants implemented in a commercial office setting. For the daylit perimeter zone, where the lighting systems included luminaire-level daylight dimming, we found that circadian criteria required no extra lighting energy. For the interior zone, meeting circadian criteria required increased lighting energy, from 11% to 42%, relative to the non-tunable LED baseline operated for photopic illuminance criteria only. Even at the higher energy levels required for circadian criteria, the systems still saved an estimated 66% relative to typical fluorescent systems in existing buildings. For specifying efficient lighting systems and designs to meet visual and circadian criteria, we recommend emphasizing daylighting where possible and selecting LED solutions with high photopic efficacies and high melanopic daylight efficacy ratios (m-DER), which can reduce the incremental energy cost of circadian performance requirements.