LBNL - FLEXLAB Study of Connected Tunable White LED

This project evaluated tunable white LED fixtures (troffers and pendants) with integrated controls, including daylight dimming, to determine visual and circadian performance and energy usage in commercial office space. The analysis culminated in information/recommendations for connected, tunable systems and strategies that optimize visual lighting performance, circadian stimulus, and EE.

Significant research efforts in the last 20 years have been conducted on the non-visual (or non-image forming) effects of light, including on human circadian health. In the early 2000s, scientists identified novel photoreceptors (Intrinsically Photosensitive Retinal Ganglion Cells, or ipRGCs) in the eye involved in circadian regulation [1], and we now understand that exposure to adequate light during the day is crucial for circadian health (physiological synchrony with the day/night cycle). Based on this understanding, circadian design is becoming a new priority for office lighting systems. This research showed that circadian criteria can incur incremental energy costs, as detailed in the Key Findings section of this report. However, with the low energy intensities of LEDs, especially relative to existing building fluorescent systems, prioritizing energy savings over circadian performance may not be necessary. For customers who choose to pursue circadian goals in new construction or retrofit lighting projects, the aim should be to minimize incremental energy cost. The lack of “official” consensus-based standards around circadian lighting design at this time remains a serious hurdle for the lighting community. Nonetheless, from the standpoint of regulators, utilities, and efficiency program implementers, it would seem prudent to provide recommendations, or even incentives, for best practices that support energy efficiency in circadian design, even while waiting for official consensus-based standards.