Lighting for Learning




Learning by Design



A human-focused approach to classroom design

In 1999, Heschong Mahone Group laid to rest a highly disputed question in school design: Does student performance improve with access to daylight? Lisa Heschong and her team concluded that student test scores do, in fact, increase with exposure to daylight,[1] but what is it about daylight that improves student performance? This article seeks to explain the connection between daylight exposure and biological functions, drawing on recent research in office design to suggest applications for the design of learning environments.

Human Evolution and Circadian Rhythms

Most of our history as humans took place outside. Our tasks, behavior, and routines were dependent upon our experience of natural elements, including exposure to the sun. The presence or lack of daylight created the temporal boundaries that moderated our daily lives. Activities were performed during the day, while rest occurred in darkness. Over time, our biological systems were programmed to respond to this—a dynamic light source that is intensely blue during the morning and slowly fades to orange in the evening before darkness. Fast forward thousands of generations of human evolution and a string of inventions, beginning with electricity, fundamentally changed our relationship with light. We are now capable of spending vast amounts of time indoors and recent studies have shown that people are capitalizing on that opportunity. A study published in 2001 conducted by the EPA concluded that the average person now spends 87 percent of their life indoors.[2]

Our body’s ability to effectively regulate our circadian rhythm, or our sleep/wake cycle, vastly declines without the presence of specific wavelengths of light at certain times of the day. For the healthy function of our circadian rhythm, high intensities of light rich in the blue-green portion of the visible spectrum are required in the morning hours to halt the release of melatonin, the chemical that initiates the sleep portion of our cycle. Later in the day, our body needs a reduction of this blue-green light to slowly begin the release of melatonin to ready itself for bed.

Broadly speaking—for many teachers, students, and office workers—the indoor environments we spend most of our lives in are less than ideal for promoting our biological functions and rely heavily on electric light illumination to allow us to perform tasks. In other words, we have sufficient light for the rods and cones in our eye to generate an image allowing us to type on a keyboard, but other photoreceptors, such as the ganglion cells, may be under stimulated. These biological goals are not necessarily unachievable with electric lights, but the current pedagogy of lighting design lacks careful consideration of the intensity, wavelength, and duration of light that is specifically entering each occupant’s eyes.

Research in Action

Humans have made significant progress toward understanding our own circadian rhythms, including a 2002 publication by neuroscientist David Berson detailing the ganglion cells’ role in modulating our circadian rhythm. [3] More recently, researchers at Rensselaer Polytechnic Institute (RPI) [4] and the University of Manchester [5] have quantified the relative stimulation of the ganglion cells with respect to different wavelengths of the visible spectrum. Most notably, Jeffrey C. Hall, Michael Rosbash, and Michael W. Young received the Nobel Prize in Human Physiology in 2017 for their discovery of how organisms synchronize their biological functions with the rotation of the earth. As these recent studies suggest, there has been significant interest from the scientific community in circadian rhythms and, with that, a new wealth of knowledge detailing human internal clocks. We now know more comprehensively how our circadian systems function biologically, and as a response, architects and engineers are beginning to implement new strategies that weave these new scientific findings into the built environment.

In an effort to engage these concepts in our own architectural practice, Seattle-based architect and daylighting specialist Marty Brennan and I set out to develop a method of simulating the annual effects of multiple additive light sources on office workers’ ganglion cells.[6] What started as an effort to create an iterative design tool for our use in practice resulted in a study considering a wide range of conditions in which millions of office workers spend their daily lives. We modeled and simulated the office environment in which we were working—fit with abundant window area and a narrow floor plan placing each desk in close proximity to those windows. The published research paper details an exploration adjusting parameters of office location, room orientation, and furniture layout. In total, we analyzed 864 different views for every hour of the year between the hours of 9 a.m. and 1 p.m. These hours were chosen, along with the threshold of blue light sufficient for circadian response, at the recommendation of the International WELL Building Institute, an organization that advocates for healthy building design and construction. [7]

The results of the study showed that of the 36 different rooms considered, not a single scenario provided each of the 24 occupants with the prescribed amount of circadian light from daylight and electric light alone. When we increased the color temperature of the electric lights to 6500-kelvin, rooms showed a significant improvement. Though our initial tests seemed dismal, adding illumination from computer monitors and task lights allowed some room scenarios to adequately perform. In a separate study, we optimized the location of the electric light fixtures, which lead to even larger performance gains, illustrating that there is a possibility for existing buildings with poor solar exposure to perform at a high level if designed correctly. The design tool later allowed us to quickly make educated decisions during the design process to positively affect the health of a room’s future inhabitants.

Designing for Education

In the most basic sense, daylight is “circadian light”—it is the light source under which humans evolved. I pose that the findings detailed by the Heschong Mahone Group in 1999 illustrate that sufficiently stimulated ganglion cells ultimately lead to an improvement in student performance. Given this finding, designers should endeavor to understand the impact their design decisions have, striving to improve student health and performance. The remainder of this article will demonstrate a practice-based exploration applying the workflow developed for our research paper within the context of a typical middle school classroom to understand the effect of a single decision on the annual circadian response of students. (See Figure A for classroom floor plan)

Figure A: 30 students were placed in a typical south facing 936 SF classroom. Light fixtures were located to provide an evenly distributed task-based illumination scheme typical of classroom design.

In this exploration, I simulated the circadian light falling onto each of the 30 students’ eyes for each hour of a year utilizing the WELL’s V1 threshold of 200 EML (Equivalent Melanopic Lux) between the hours of 9 a.m. and 1 p.m. as the quota of circadian light. The simulation compares a baseline scenario against a scenario utilizing an exterior shade to control daylight-induced glare. The exterior shade was designed in a separate study to maximize its performance.  The modeled environment is intended to be as typical as possible in an effort to display the relative impact of the exterior shade, not to illustrate an ideal classroom. A 6500-kelvin sky was coupled with 3000-kelvin electric light fixture for this study.

Figure B: The parameter adjusted in the study was the use of an exterior shade, consisting of three 18” louvers that are minimally intrusive to exterior views. The room that included an exterior shade saw a 22% increase in performance.

New Ideas, New Future

The test results indicate that adding the exterior shade results in an average 22 percent increase in hours meeting the quota for students annually—illustrating that a reduction in daylight caused glare improves occupants’ circadian health. After digging through simulation data, I found this to be a byproduct of decreased blind use, which allows for more hours of diffuse daylight to enter students’ eyes. Looking at the visualized results in Figure C, you can see that the students lighting conditions are heavily driven by their view of the different light sources. Students on Liam’s side of the room far away from the windows have inadequate circadian lighting, while students near Zoe have their healthy dose.

If we take, for example, Leah’s lighting conditions (Figure C), we see a 10% jump in hours meeting her quota with the added exterior shade. For Leah’s position in the room, I also conducted a separate study to test the improvement of using a 6500-kelvin light instead of a 3000-kelvin fixture, which resulted in a 15-20 percent increase in her lighting performance. If we kept optimizing other parameters, you can imagine that before you know it, Leah is meeting her healthy lighting quota for the whole year.

Figure C: Each student is represented with two cylinders: an orange one representing the performance in a scenario utilizing the shading device, and a blue cylinder representing the baseline scenario without exterior shades. The cylinders are extruded to visualize the percent of time that 200 Equivalent Melanopic Lux are reaching the student’s eye during the testing hours of 9 a.m. to 1 p.m. annually. A taller cylinder represents increased ganglion cell stimulation.

In many ways, the lighting conditions of many classrooms represent a massive departure from the very environment under which we evolved—trading abundant daylighting opportunities for ill-performing florescent tubes. This study is not intended to conclude that simulation is required in every design process, but rather to illustrate the potential effect a single decision can have on the biological health of thousands of children for many years to come. Small, simple choices compound to solve large, complex problems. If we simply expand our current task-based understanding of light to include biological sustenance, we can create a brighter future for both our children and educators.


[1] Heschong, Lisa, et al. “Daylighting Impacts on Human Performance in School.” Journal of the Illuminating Engineering Society, vol. 31, no. 2, 2002, pp. 101–114

[2] Klepeis, Neil E., et al. “The National Human Activity Pattern Survey (NHAPS): a Resource for Assessing Exposure to Environmental Pollutants.” Journal of Exposure Science & Environmental Epidemiology, vol. 11, no. 3, 2001, pp. 231–252

[3] Berson, D. “Strange Vision: Ganglion Cells as Circadian Photoreceptors.” Trends in Neurosciences, vol. 26, no. 6, 2003, pp. 314–320.

[4] Rea, Mark S., et al. “Circadian Light.” Journal of Circadian Rhythms, vol. 8, 2010, p. 2.

[5] Lucas, Robert J., et al. “Measuring and Using Light in the Melanopsin Age.” Trends in Neurosciences, vol. 37, no. 1, 2014, pp. 1–9

[6] Martin, Brennan, and Collins, Alex. “Outcome-Based Design for Circadian Lighting: An Integrated Approach to Simulation & Metrics.” ASHRAE, IBPSA-USA, 2018 Building Performance Analysis Conference and SimBuild, 2018, pp. 141–148.

[7] International WELL Building Institute. 2017. The WELL Performance Verification Guidebook, Q2 2017., Accessed March 2019

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