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Daylighting Tips and Strategies for Existing Buildings
The Chicago office for HKS, an international design firm, takes maximum advantage of natural daylight. Photo courtesy of Tom Harris.
Increasing the use of natural light in an existing building can be difficult—you can’t exactly cut new windows into the side of an occupied building without disrupting operations and incurring major costs, and some spaces are simply too far from the windows to benefit. But there are a few things you can do to maximize your use of natural light wherever you are able and use artificial light efficiently in the rest of your space.
[Related: 3 Tips for Daylighting Integration]
Why Maximize Daylighting?
The benefits of daylighting are well-documented. In addition to reducing your need for artificial light, thus lowering your energy costs, the use of natural light has been associated with reduced eye strain, improved mood and lower fatigue for occupants.
“Natural light really benefits occupants’ wellbeing,” explained Allison Smith, sustainable design leader for HKS. “We know it supports the circadian system, which has so many different physiological benefits. We’re most closely aware of how it supports us in having better sleep.”
Achieving a good balance between natural and artificial is a constant challenge, Smith added. Artificial light is typically the same all day, but “natural light is constantly changing throughout the day and year, and it’s also dependent on weather,” she said. “Keeping that balance with the artificial light can be a challenge because it is constantly changing.”
[Related: 4 Ways to Control Daylight]
6 Daylighting Strategies for Creating Better Spaces
Despite the challenges, there are a few things you can do to create more comfortable spaces that make good use of whatever daylight is available. For example:
1. Make sure your ceiling and walls are reflective enough. “For an office-type space, we really want to target a relatively high reflectivity on the ceiling—85% or greater,” Smith said. “On the walls, we’re looking for a mid-level reflectivity of about 60%. For flooring, we don’t want to have a lot of reflectivity or glare, so we’re looking for a darker floor.”
2. Do your own daylighting audit. Scott Bowman, BOMI instructor, LEED Fellow and engineer at IDEABuildWorks, suggested investing in a light meter that can show you how many footcandles or lux are falling in different areas. “Do that on a Saturday or Sunday when you can turn the lights off, because you’re going to want to look at certain times of the day to see how your south and north faces are working,” he said. “Compare that to what it is at night when you have the lights on. That will give you an idea of how many footcandles you’re putting onto worksurfaces. That will at least tell you whether you’re in the ballpark [of having enough footcandles from daylighting], and that’s something you could present to a lighting designer to get their opinion.”
3. Taper light levels depending on how much light is coming into the space. Zone your lighting appropriately so you can scale back the artificial lighting in spaces that are receiving adequate natural light.
4. Consider occupants’ needs. Some people may prefer more light on their workspaces than the Illuminating Engineering Society’s standards for light levels require. Instead of increasing the light levels coming from the overhead lighting, consider providing task lights or other personal control for people who need it, Smith suggested.
5. Try window films. Some window films now on the market are able to bounce daylighting deeper into a space, Bowman said. The film is installed in the upper portion of the window and redirects daylight toward the ceiling, diffusing it into the space.
6. Mimic natural light in spaces that can’t get any daylight. Subterranean spaces and core areas far from windows will never be able to get enough natural light despite your best efforts around window areas. For these spaces, Jeff Hungarter, director of indoor lighting for Cree Lighting, suggested investing in dynamic skylights that change color temperature and light intensity depending on the time of day. These can help employees reap some of the benefits of natural light in spaces where real daylight never reaches.
Increasing the use of daylighting in an existing building can be a tall order, but the energy savings and effects on occupants can be well worth it. Evaluate your building to see whether it’s a candidate for more natural light—you may have much to gain by letting the sunshine in.
Read next: How Light Shelves Maximize Daylighting