WELL Design Series: Lighting for Circadian Rhythms and Mental Health

The concept of an integrated design approach – one that interlaces multiple disciplines to inform the design and construction of a space – is not a new one (we’ve been practicing this way at RDG Planning & Design since our founding). We know that presenting a series of choices and solutions early in the design process can create an orderly flow to interdisciplinary dialogue and ensure all members of the design and delivery teams participate fully and constructively. As the WELL Building Standard becomes increasingly well known, it’s elevating the idea of integrated design and pushing these diverse groups to make design decisions that benefit both building occupants and the environment equally. This is true for every stage of design, including lighting design.

In previous articles in this series, we explored how the WELL Building Standard impacts various environments, from workplaces to senior living communities. We know that incorporating WELL design into a building can positively affect users’ health and well-being by encouraging movement, emphasizing healthy eating and drinking options, and ensuring thermal comfort. Our exploration of WELL design ends with this fourth and final article and addresses WELL Light concept and how integrated teams can create environments that are visually balanced and offer enriching places to work, live and study.

WELL Lighting Concept Features

Light is the main driver of the visual and circadian systems. As light enters the human body through the eye, it’s sensed by photoreceptors in the retina that are linked to the visual and circadian systems. Given that people spend much of their waking day indoors, insufficient illumination or improper lighting design can lead to drifting of the circadian phase, especially if paired with light exposure at night. Lighting environments impact the visual, circadian and mental health of humans, and while most environments are designed to meet the visual needs of individuals, they often don’t take into account circadian and mental health. WELL Light concepts aim to address this by promoting exposure to light and providing lighting environments that reduce circadian phase disruption, improve sleep quality, and positively impact mood and productivity.

The Lighting Concept Features in WELL v2 focus on human exposure to artificial and natural light. Unlike the lighting power density (LPD) calculations done for energy efficiency compliance, the lighting solutions for WELL require input from both architects and interior designers as part of the process. As design teams work together to incorporate WELL lighting concepts, it’s helpful to have a deeper understanding of these features. Here, we break them down in greater detail.

Light Exposure and Education (LO1). This WELL feature requires projects to ensure appropriate light exposure in indoor environments by using daylighting or electric lighting strategies. By providing indoor access to daylight, an architectural environment can positively influence the productivity and mood of individuals, while supporting the alignment of circadian rhythms with the natural day-night cycle. This is especially important in the northern climates, where there are more cases of Seasonal Affective Disorder (SAD) caused by a lack of exposure to daylight due to long nights and increased time indoors during the coldest parts of the year.

To encourage users to seek light exposure on their own, LO1 also stresses the importance of educating building occupants on the importance of light and how it affects their biological, physiological and psychological well-being. WELL projects should provide educational resources to occupants that explain health-related concepts such as circadian rhythms, sleep hygiene, age-related increase in light requirements and the importance of daylight exposure. These materials could range from training and videos to brochures and newsletters. The key is to empower users to better understand how light impacts their overall well-being.

A WELL Lighting Tip: The human biological clock needs periods of darkness to reset and keep the circadian cycle “in rhythm.” Encouraging building occupants to avoid screen time at least one hour before bedtime and minimize exposure to other light sources during the night to help biological systems “rest and reset,” will allow individuals to awake refreshed with the next day’s solar cycle.

Visual lighting design (LO2). The goal of every lighting designer is to provide a comfortable visual environment for occupants of the built environment. WELL’s visual lighting design feature reminds the lighting designer that design decisions and solutions need to take into account illuminance standards and ensure lighting design solutions consider both the age of occupants and the tasks they’ll be performing. As an example, there is no single design solution for an “office” project type, but rather a need to critically look at the kind of work being done within the space. When designing for a law office, for instance, lighting needs to support paper-driven analog tasks; a call center, on the other hand, should be optimized for heavier electronic use.

Circadian lighting design (LO3) and enhanced daylight access (LO5). These WELL features concentrate on daylight visibility (access) of the building’s occupants. As we discussed previously, daylight is responsible for our circadian clock and the regulation of most of our biological systems. Circadian rhythms are kept in sync by various cues, especially light the body responds to that is facilitated by intrinsically photosensitive retinal ganglion cells (ipRGCs), or the non-image-forming photoreceptors of the eyes. Accordingly, humans have evolved to base our circadian rhythms around the natural light/dark patterns associated with daytime and nighttime. Building design and interior space planning have a substantial impact on the amount of daylight available to occupants in an indoor space, and an integrated design team should consider indoor daylight access during all stages of building planning, from architectural and façade design to interior design and layout. 

A WELL Lighting Tip: Even with the best design intent, being indoors for an extended time often does not provide humans with the recommended amounts of exposure to daylight. If the occupants can’t be exposed to daylight, then the building’s lighting designer needs to consider ways to “dose” the occupants with lighting that simulates the duration, color and intensity of natural light. 

Glare control (LO5) and visual balance (LO6). WELL Features L04 and L06 focus on how light is presented in the interior environment. Feature L04 focuses on glare from both daylight and artificial light. In the past, cathode ray tube computer (CRT) monitors had highly reflective curved glass fronts, proving just as problematic as direct source glare. Indirect lighting systems of the past attempted to rectify the glare issue, however, these systems more often resulted in eye fatigue due to lack of contrast and lower-than-recommended lighting levels. Though the pendulum has swung the other direction, and we now use flatscreens in most office applications, even these updates don’t completely resolve the glare problem. The architectural trend of small, narrow aperture linear fixtures produces far too many lumens out of a small aperture, resulting in many of the same visual discomforts: high contrast from dark ceilings and walls in comparison to the extremely bright apertures of these fixtures. What’s more, dimming these lighting sources can reduce recommended lighting levels, so many building occupants find themselves in a no-win situation.

Feature L06 attempts to find a “balance,” recommending contrast ratios between lit areas, wall surfaces, ceilings and tasks. Ideally, the interior designer and lighting designer are working together to ensure visual balance through careful space planning and focus on the reflectance values of various finishes within the visual field of the occupants.

Our designers put these WELL features into practice when our team designed lighting for a major financial corporate call center. The building was a large open office environment, and there were no windows in the space due to requirements that it be able to withstand tornadoes and other natural disasters. Knowing that productivity and morale would be affected by the visual environment, the lighting team worked closely with the architecture team to develop a perimeter lighting system that created a bright vertical element (wall wash) and utilized indirect/direct pendants to provide both ambient and task lighting in the space. This “volumetric” approach to the lighting helps diminish the negative effects resulting from a lack of exposure to daylight yet still provides high luminance levels for the building’s occupants.

Electric light quality (LO7). Feature L07 is the most straightforward of the features in that it requires the lighting designer to use high-quality sources that produce good color rendition, color quality and that have minimal flicker. The best outcomes produce a fairly consistent artificial light source that can mimic the quality of daylight experienced outside the built environment.

A WELL Lighting Tip: Budget constraints will require designers to closely analyze their lighting fixture schedule and specifications and find a balance between cost and high-performing sources. By including requirements for TM-30 data and high-quality sources in fixture selection analysis, lighting designers can establish a straightforward set of recommended specifications that apply to most interior lighting situations. As specifiers and manufacturers transition from CRI to TM-30, these specifications should result in tangible changes across the industry, which in turn will bring additional competition to the market. By insisting on these metrics, lighting designers can advocate for broader choices within the market.

Occupant control (LO8). The final lighting feature in the WELL standard incorporates elements of all the others, reminding lighting designers every person has unique needs and wants regarding lighting. Users require control of their lighting environments, and providing some measure of autonomy around lighting control, including color, intensity and color temperature of the lighting within their environment, can help create equity. During the COVID-19-era, many of us have actually gotten used to having control, as we regularly adjust the lighting, thermostat, ambient noise, etc. of our home offices.

Once we return to a fixed office environment, we may find it difficult to adjust to not having that personalized control of our environment. To counter this, designers can incorporate task lights at workstations, which allow for some controllability of a worker’s individual space. Greater control in larger open office environments may take additional time and resources, but managers and facilities groups should work together to understand how allowing individual levels of control can help raise moral and worker productivity.

WELL v2 draws expertise from a diverse community of WELL users, practitioners, public health professionals and building scientists around the world. As with all WELL features, an integrated design team is key to managing and implementing these features, and lighting designers can provide critical knowledge and expertise around the lighting topics presented in this article. 

Ultimately, lighting is much more than fixture selection and arranging rectangles and circles on a reflected ceiling plan. True lighting design focuses on the entire three-dimensional visual environment and how it will affect the biological and psychological well-being of the building’s occupants. Because we’re limited, both by energy codes and by the intricate nature of the human visual system, design teams must work to find balance and design spaces that are both visually balanced, and offer users enriching places to work, live and study.