With this knowledge, the role of the specifier also includes keeping the health impacts of lighting in mind as they work on projects. Who are the people that will be spending the most time in each building and what are their specific needs? Offices, daycare centers, hospitals, retirement homes, and more, all have benefits they can reap from proper lighting.
Daytime light versus nighttime light
While it may sound like a cliche, the truth is, not all light is created equally. Different types of light signal to the brain when it is time for specific activities and energy levels. Therefore, different lighting is needed during the day than at night.
There is a new metric, which determines how healthy light is, known as vertical melanopic equivalent daylight illuminance (EDI). Melanopic EDI (m-EDI) is a measurement adopted by the International Commission on Illumination (CIE) that captures the full impact of light and how the body perceives it. There has been a push in the lighting industry to set a precedent in circadian lighting and m-EDI is finally the measurement to help establish this guideline.
The agreed upon scientific recommendation, and WELL Standard, is receiving a minimum of 250 m-EDI vertically at the eye during the daytime, rich in blue spectrum to simulate daylight. This baseline gives designers a way to create spaces that provide an appropriate amount of light.
Unfortunately, because m-EDI is a new measurement (developed over the past five years), much of today’s traditional or existing lighting only gets 35 percent of the light needed for optimal wellbeing. Color tuning solutions will increase this to 50 percent of the wellness criteria. Again, woefully short of meeting one’s daily needs. Even windows have a difficult time reaching these criteria.
Based on the author’s research, to get enough light from windows, one needs to be facing it directly. Facing a wall next to a window will only yield about 50 percent of the criteria. The measurement, m-EDI, proves it is not enough to merely dim the lights or change the temperature to get the proper m-EDI needed; the light spectrum, direction, and color of the light must be taken into consideration.
Further details on how these factors play a role is illustrated here. Note: currently it is not mandatory to meet these criteria, but support for these criteria is expected from the Illuminating Engineering Society (IES) and the International Commission on Illumination (CIE) by 2024.
The human eye is looking for high amounts of vertical m-EDI during the day and low amounts at night. A blend of sun and sky will give a person the most m-EDI, making it the most beneficial for daytime use. High m-EDI during daytime boosts productivity, decreases depression, improves mood, energy, and alertness. For office spaces in particular, circadian lighting should be taken into consideration, aiming for a minimum 250 EDI (as mentioned earlier), and it is best to incorporate lighting gradients with cooler tones and blue light to optimize workers’ energy and focus. With more companies transitioning to remote work or offering hybrid models, the same can also be considered for residential buildings.
For nighttime, the lighting should be as warm as possible with a maximum of 10 EDI about two to three hours before bed. Finally, at night, when sleeping, the darker the better. Fully removing any blue light exposure and maintaining a maximum of one EDI. Think of a natural sunset with its warm tones and gradients; red or amber light promotes natural melatonin production, building relaxation and sleepiness, which helps in winding down for bed.
