Illuminating Design Strategies for Daylighting
In our continuing series on high-performance design features, we’re exploring the effects views, daylighting, indoor air quality, thermal comfort, and acoustics have in producing significant positive impacts on workplace productivity. Though we are exploring each feature individually in these installments, we consider these design features holistically in our high-performance design practice for workplace, which focuses on complementary strategies proven through research to improve health and wellness of users. As an integrated strategy, how much does daylighting matter, and how should designers design for useful natural light?
How Much Does Daylighting Matter?
Research that studies daylight in isolation without other variables such as views is hard to find because it is rare to find these elements in isolation. Citations specifically mention that daylight “helps set our circadian rhythm” and that “sunlight is important for mood.” Even when the workplace has sufficient artificial lighting for employees to see well and perform their daily tasks, occupants may still not be getting adequate sunlight exposure to support healthy circadian rhythms.
In winter 2013 and summer 2014, Mariana G. Figueiro and Mark S. Rea studied lighting in an office building in Colorado and the impact of personal light exposures on sleep and mood in two seasons.1 This study examined the links between an employee's exposure to natural daylight during summer and winter, and individuals’ mood and sleep. The researchers found that while artificial lighting was supportive for the work tasks at hand, employees still suffered from lower moods and less restful sleep in winter when the windows provided less natural light.
JE Dunn in Minneapolis by DLR Group. Photo by Brandon Stengel.
A study conducted by Jeanne F. Duffy and Charles A. Czeisler in their paper Effect of Light on Human Circadian Physiology investigated the effects of light on the human circadian timing system.2 These studies have revealed how the timing, intensity, duration, and wavelength of light affect the human biological clock.
In a 2010 study, psychologist Julian Thayer and his team compared human performance in an older workspace with limited access to windows to a newer workspace with better views and increased exposure to daylight.3 The outcomes revealed that workers in the new space had lower markers of stress and improved indicators of heart health. The workers in the new space also exhibited a better sleep cycle and lower stress outside of the workplace.
Studies that incorporated views and daylight both were highlighted in the previous Insight, The View on Workplace Design:
- A 2011 study by Ihab Elzeyedi examined an open-plan office building at the University of Oregon. The study linked a 10 percent reduction in occupant sick days to both view of nature and exposure to daylight.
- In 2003, the Heschong Mahone Group undertook a major study with the Sacramento Municipal Utility District to study the performance of employees. Employees with views and sunlight access handled calls 6-to-12 percent faster and performed 10-to-25 percent better on mental function and memory tests.
- In 1994, Joseph J. Romm and William D. Browning studied ING Bank’s new headquarters, where all individual workstations were located within 23 feet of a window with access to views and daylighting. Romm and Browning identified a 15 percent reduction in absenteeism.
Sato Elementary School in Beaverton, Oregon by DLR Group. Photo by Josh Partee.
This research, and other studies like it, highlights the benefits of daylighting to offer end users reduced absenteeism, lower stress, and improved performance and mental function. All of these factors may indicate a more productive environment where user performance is enhanced.
How to Design Spaces for Useful Daylight
There are three aspects to keep in mind when focusing on daylight and design. The first is designing for adequate daylight, or foot candles, in a space per Illuminating Engineering Society standards to maximize the benefits of natural light and lighting energy savings. The second is designing to support human circadian rhythms, or biological clocks, which is dependent on timing, intensity, duration, and wavelength of light delivery. The third is using daylight to enhance biophilia, related to the school of thought of bringing humans back to contact with nature. Daylighting is a large part of what provides people access to the natural environment.
The top five facets of designing to optimize daylight are as follows.
Nelnet at Telegraph District in Lincoln, Nebraska by DLR Group. Photo by Paul Brokering.
Building orientation and external shading for windows can ensure access to glare-free, useful daylight. Providing external shading ensures that glazing will be shaded from direct sun, or glare, allowing internal shades to stay up and preserve comfortable access to natural light.
West-MEC Northeast Campus in Phoenix by DLR Group. Photo by Anna and Faithie Ekbundit.
Building form and depth lays the foundation for access to daylight. Limiting the depth of the building so the deepest workstation is less than twice the height of the window from the perimeter can provide enormous opportunities for natural light penetration. Limiting the depth of the space, if daylit from one elevation alone, also ensures more uniform daylighting in the space. If daylighting is not uniform, the space can appear glaring even when foot candle levels are met. To improve the uniformity of daylight, provide glazing on two perpendicular walls or provide skylights.
Adjustable Forms in Lombard, Illinois by DLR Group. Photo by James Steinkamp.
More glazing is not more daylight. Glazing should be strategically located to maximize uniform daylight in the space. Windows providing natural light should be closer to the ceiling height as these will permit light to penetrate deeper into the space. Daylit windows should be placed strategically to reflect off vertical surfaces. This tends to brighten the vertical surfaces, making the space feel brighter and well lit.
Missouri Innovation Campus in Lee's Summit, Missouri by DLR Group. Photo by Michael Robinson.
Selecting the right glazing and technical specifications is key to achieving glare-free daylighting. Glazing specifications to consider include visible light transmittance (VT) and solar heat gain coefficient (SHGC), which limits heat gains in interiors. These attributes often conflict, so it is key to find glazing that can give you a lower SHGC with a high VT. In some climates however, VT does not have to be very high to achieve the daylighting levels required. In this case a tint, along with a low-e coating, can help reduce the SHGC. If direct sun can contribute to glare, consider including a translucent layer between sheets of glazing to diffuse glare-free light into the interior.
@9 Amenity Center in Minneapolis by DLR Group. Photo by Brandon Stengel.
Surface reflectance, for both interior and sometimesexterior, can have a huge impact on daylight perception and foot candles in the space. The ceiling reflectance should be the highest, greater than 80 percent, with the walls being the same or close at greater than 70 percent. Some spaces that face external surfaces also depend on the reflectance of these surfaces for natural light, so having a lighter color exterior can enhance daylight in these spaces. The same can also be true for external ground reflectance in certain conditions.
Setting a goal for daylighting is key to achieving it. Setting goals for a percentage of employees to access natural light may be more effective than prioritizing a percentage of square feet with daylight. Most certifications such as LEED and WELL give design credit for glare-free daylight, and can help set the criteria for meeting your goals. It is however important to evaluate the daylighting performance quantitatively, as well as qualitatively, since these standards have been written for all climates and building types. Your project may have nuances that are not captured in these standards alone.
Designing to optimize daylight is one strategy to enhance the human experience through design. Read how we leverage research to support our client and end user goals for optimizing views.
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- Figueiro, M. G., & Rea, M. S. (2016). Office lighting and personal light exposures in two seasons: Impact on sleep and mood. Accessed at http://journals.sagepub.com/doi/abs/10.1177/1477153514564098.
- Czeisler, Charles A. & Duffy, Jeanne F (2009). Effect of light on human circadian physiology. Accessed at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717723/.
- Thayer, J. F., Verkuil, B., Brosschotj, J. F., Kevin, K., West, A., Sterling, C., ... & Marques, A. H. (2010). Effects of the physical work environment on physiological measures of stress. European Journal of Cardiovascular Prevention & Rehabilitation, 17(4), 431-439. Accessed at: http://journals.sagepub.com/doi/pdf/10.1097/HJR.0b013e328336923a