Dr. Octavio L. Pérez holds a Ph.D in Multidisciplinary Science from Rensselaer Polytechnic Institute (RPI), Troy, NY, USA. His field of interest is HCL (human centric lighting) and its application in the healthcare environment. He conducted his doctoral research at Mount Sinai Hospital in New York City focused in the effects of lighting in clinician wellness and performance, and patient safety. Now he is affiliated with Mount Sinai, and he is developing the HCL business intelligence and strategy for one of the key lighting manufacturers in Europe.
Melanopic Photometry vs. Melanopic Lux – The WELL Standard as a Case Study
Octavio L. Pérez, PhD, HCL Senior Scientist and HCL Business Developer at Lledó Lighting (Spain), and Patient Safety Adjunct Researcher at Mount Sinai Hospital (New York, NY, USA)
Justiniano Aporta, PhD, Professor in Optics / Applied Physics, University of Zaragoza, Spain
Since the first published evidence of the non-visual photoreceptors in 2002, many models have been proposed to measure the effect of light in humans. Different versions of the melanopic lux concept have been published. Recent building standards, such as WELL, propose to incorporate the circadian effects of light into the building certification process. WELL proposes the melanopic equivalent lux (MEL) as the evaluation metric, but there is a need of clarification of how the MEL has to be measured.
Lighting practitioners and manufacturers need tools to be able to apply scientific and academic research into daily practice. We propose in this study the application of a model based on solid photometric methods that will contribute to an appropriate application of the design, evaluation and ultimate certification process.
Our method is based in the conventional photometric approach, taking into consideration the special characteristics of the melanopic lux. We take as a case study the model proposed in WELL, the melanopic equivalent lux (MEL). It is based in the Lucas model modified for the aging eye.
We develop conic profiles and polar maps of fixtures. This will help to introduce the melanopic lux in standard software for photometric calculations, and get practical melanopic illumination data in the lighting environment.
We use these three fixtures in real office environment at different settings for three specific HCL scenes: early morning cool white (6500K) with high melanopic stimulus (470nm); after lunch (post-prandial) neutral white (4000K) with medium melanopic stimulus, and evening warm white (3000K) with no melanopic stimulus but enhanced rod stimulus (505nm).
Three different datasets will be presented and discussed: the spatial spectrophotometric (SPD) data of three innovative HCL fixtures under the melanopic perspective, the lit environment data of a real office environment where these fixtures are used under three HCL scenes/presets, and the lighting certification validation study following the WELL standard.
We have performed in the photometric laboratory the spatial spectral (SPD) study of three innovative HCL fixtures that are tunable white (2750-6500K), and have also specific HCL spectral content (470nm and 505nm). This melanopic photometric data will be shown in familiar photometric figures and tables, such as the conic and polar diagrams. This will be the basis data to study and evaluate the lit environment from a HCL perspective to improve human wellbeing and achieve wellness certification (such as the WELL standard).
We present the melanopic photometric results of the three settings as it will be calculated to help lighting professional simulate and prescribe the lighting environment to maximize HCL contribution and to obtain WELL certification in the office setting.
The melanopic lux model has been introduced, and adopted in building standards such as WELL, to evaluate light impact in human health and wellbeing. There is a need to incorporate this concept into photometric practice to properly prescribe lighting settings, and to evaluate and certify lit environments according to building standards that consider circadian lighting.
WELL is the first building standard that proposes a circadian metric, the melanopic equivalent lux, as a requirement to achieve certification, but there is a lack of photometric models to properly evaluate the lighting environment.
This study contribute to apply and evaluate circadian lighting in the office environment.
A limitation of the study, that is a fundamental limitation of the melanopic lux model is the lack of consideration about the directionality of the lit environment. It is known that light affects the eye differently depending on the spatial exposure, having maximum effect in the lower and nasal areas of the eye. This limitation has to be addressed in future research.