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Designing for Health: Light – The WELL v2 Standard

by Jon Young, LEED AP BD+C, WELL AP, Sustainability EIT II

“Light is necessary for life, and artificial light improves visual performance and safety, but there is an increasing concern of the potential health and environmental impacts of light. Findings from a number of studies suggest that mistimed light exposure disrupts the circadian rhythm in humans, potentially causing further health impacts.”

– US National Library of Medicine, Systematic Review of Light Exposure Impact on Human Circadian Rhythm

Alive + Well, Designed by Matt Fajkus Architecture (Bee Cave, Texas)

Humans have evolved over time to synchronize our internal clocks with the rising and setting of the sun. This 24-hour physiological cycle is known as our circadian rhythm, and it plays a significant role in our sleep, mood, mental health, healing, and recovery time.

Because natural and artificial light are the main drivers of our circadian rhythm, the way we design glazing and lighting systems in the built environment has far-reaching implications on both our individual health and the overall well-being of our communities. So, what are the important things to consider when designing a lighting environment to support a healthy physiological response?

To maintain a healthy circadian rhythm, the body requires certain amounts of light during the day and certain amounts of darkness at night. When designing lighting systems, the WELL Standard recommends looking at the ambient intensity of light, brightness contrasts, glare control, high-quality color rendering, design strategies for interior surface reflectivity, automated shading, and dimming controls, and appropriate incorporation of daylight.

The Terminal at Katy Trail, Designed by Michael Hsu Office of Architecture (Dallas, Texas)

Health and Well-Being in the Built Environment, Concept 4: Light

Issue: Exposure to light is the main driver of our circadian rhythm. Poor lighting environments can cause irregularities in wakefulness during the day and tiredness at night. Lighting design can also impact our mood and the amount of strain on our eyes. Given that we spend most of our waking day indoors, the way in which we design our lighting in the built environment plays a significant role in our mental health, cognitive performance, and sleep patterns.

Health Implications: Improper lighting design can lead to a disruption in our circadian rhythm, poor mood outcomes, decline in cognitive function, productivity, and overall mental health. Additionally, disruption of the circadian rhythm can result in sleep loss, obesity, diabetes, depression, and metabolic disorders.

Solution: Healthy lighting design in buildings aims to provide lighting environments that positively impact our mood, circadian rhythm, sleep quality, and increase our productivity.

WELL v2 Standard’s Recommended Strategies:

  • Providing appropriate lighting exposure by requiring at least 30% of regularly occupied spaces achieve a Spatial Daylight Autonomy of sDA200,40%
  • Encouraging users to seek light exposure on their own by providing newsletters or educational signage in high traffic areas about the importance of light for our health
  • All indoor and outdoor spaces to comply with lighting recommendations from the IES Lighting Library, EN 12464-1 standard, ISO 8995-1 standard, or GB50034-2013 standards
  • Designing lighting for a healthy circadian rhythm by providing light levels of at least 150 equivalent melanopic lux (EML) between the hours of 9 a.m. and 1 p.m.
  • Utilizing glare control strategies such as predictive calculations of glare levels, choosing appropriate light fixtures for the space, and using shading techniques
  • Enhancing daylight access through indoor daylight exposure and outdoor views
  • Implementing an enhanced daylight simulation during design
  • Managing brightness in spaces to limit fluctuating light levels that may cause discomfort
  • Provide lighting which meets color rendering and quality standards such as CRI > 90
  • Allowing occupants control of lighting within their space with strategies such as task lighting to encourage interaction with their surroundings and account for personal preferences


With the rise of smartphones and streaming services like Netflix and Hulu, it can be difficult to avoid improper light exposures at night. However, support for a healthy circadian rhythm can come from the built environment by setting the tone with recommended amounts of natural and artificial light exposure throughout the day. By designing buildings with lighting systems that support a healthy circadian rhythm, we can help improve the sleep quality and the associated health impacts for ourselves, our families, and our society.

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W Hotel Nashville | HKS Architects | Nashville, Tennessee

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