A precious commodity this time of year, daylighting is nature's gift to all

Mesa Verde National Park: Spruce Tree House (Source: NPS)

As the solstice approaches, I’ve been thinking a lot about daylight. (And really, when it’s dark before I even leave the office, how can you not think about daylight?)

Because everything that’s old is new again, the coming solstice has led me to think not only about daylight but also about daylighting: that millennia-old method of lighting buildings using natural light. It turns out, in this day and age, daylighting buildings—especially buildings that are mostly occupied during normal business hours, such as schools, offices and factories—can save anywhere between 20 and 90 percent on their lighting energy compared with conventionally lit buildings.

Given that lighting accounts for 14 percent of U.S. electricity use, daylighting can effect a powerful savings, both in money and in the carbon emissions that come from power plants. Those aren’t the only benefits, though: studies document daylighting-enabled improvements in areas as diverse as the well-being of building occupants, in improved worker and student productivity, in increased retail sales, in faster healing among patients in daylit hospitals. In short, daylighting not only meets the human need for connection to the natural rhythms of the day, and for connection with the outdoors, but pays for itself many times over. In this age of climate change, daylighting also makes buildings and their residents more resilient, by providing light even when electric power isn’t available.

Time-tested resourcefulness

Today’s green builders aren’t the first people to utilize daylighting, of course. Examples date back thousands of years to groups that include the Anasazi Native Americans, who oriented their dwellings around patterns of the sun. That process increased interior lighting, blocked heat gain in summer and promoted it in winter, when it was needed most. In pre-World War II American architecture, daylighting examples abound. Manhattan’s now-tony Soho district serves as a case in point. The original cast iron factory buildings there, built in the mid-1800s, were constructed to allow maximum daylighting, with small floorplates and tall windows.

The Dark Ages

In the post-World War II period, and especially during the 1960s and ‘70s, cheap electricity (aided in large measure by policies incentivizing “energy supply gains sans environmental and social costs” for the electric utility and extractive fossil energy businesses) along with improvements in electric lighting technology led architects and builders away from the sun and all its attendant benefits, unfortunately. We can instantly recognize the worst of such buildings, which exist in nearly every American city and college campus with the characteristic smooth concrete slab nearly windowless “punch card” exterior.

Daylighting Renaissance

But now, daylighting is undergoing a renaissance in the U.S. “The architectural community has rediscovered how daylight makes spaces sparkle,” explains Vivian Loftness, a professor of architecture at Pittsburgh’s Carnegie Mellon University and one of the nation’s leading experts on the impacts of daylighting in the built environment.

Daylighting, Loftness says, can be broken down into two practices: There’s daylight harvesting, in which one uses controls to “dim the lights relative to the amount of daylight in a space,” she explains. And then there’s daylight autonomy, in which a “building is designed around daylight. These buildings are sometimes completely lit by daylight in the daytime.” Daylight harvesting can save 30-50 percent on lighting energy; daylight autonomy can save as much as 70 percent, sometimes even more.

High performance buildings harvest daylight 

The Research Support Facility at the National Renewable Energy Laboratory, outside Denver, is one such building designed to take full advantage of the sun. The net-zero office building was designed along an east-west axis, to maximize the southern and northern exposures that allow in the most utilizable sunlight. “Daylighting is about how you orient and site a new building,” explains Rob Guglielmetti, an NREL daylighting engineer who, while he worked in private industry, helped create the daylighting plan for the RSF. By and large, the 1300 NREL employees who work in the RSF love the access they have to daylight. “The comments have been overwhelmingly positive,” Guglielmetti says. “People here talk a lot about the light quality in the building: about how it feels open, how they like being able to see outside, being able to know what the weather is.” In the RSF, depending on the weather and the time of year, as much as 90 percent of the lighting is provided by daylight alone.

NREL Research Support Facility, Golden, CO (credit: NREL)

Daylighting yields big benefits for people and creates energy savings

New buildings aren’t the only ones that can install daylighting, by the way. Retrofits are becoming increasingly common, as building owners begin to understand daylighting’s many advantages.

Among them:

  • Daylighting can lead to decreases in employee absenteeism of as much as 15 percent, studies have found.
  • Students with access to lots of natural light and views of the outside world score as much as 26 percent higher on tests, compared to students in windowless classrooms.
  • Hospital patients in brightly daylit rooms required less medication than to patients in dim rooms, and have shorter lengths of stay.
  • Walmart famously conducted a study, still unpublished, in which it daylit half of one of its stores. Sales of products from the daylit half jumped by 13 percent.

“When you talk to customers about daylight stores, they don’t necessarily notice that they’re daylit,” notes Loftness. “But they’ll say things like, ‘It’s much cleaner than the other stores I go to.’ Or, ‘I found what I wanted right away.’ Or, ‘the merchandise looks so much fresher.’”

Back to employment: A 2004 study of a Sacramento utility call center found 6-12 percent faster call-handling time for employees who had views of green space from their workstations. “That’s a huge productivity leap,” Loftness says. If daylighting a new building costs more—and there’s no reason it has to. In fact, NREL’s daylit, net-zero RSF cost less per square foot to build than the average Denver-area office building—daylighting can pay for itself quickly, in increased productivity gains and decreased absenteeism. “Your workforce is the biggest expense that any corporation has,” Guglielmetti explains. “If you design a building that makes its workers happy, it saves a lot of money.”

These days, though the old standards of small floorplates and lots of south- or north-facing windows still hold, there are new technologies that can make daylighting even easier and more cost-effective in new and retrofitted buildings alike:

And new computer modeling software platforms, like NREL’s Open Studio program, allow designers and architects to model daylighting in buildings in locations around the world.

Daylighting also allows us to build and rebuild with climate resilience in mind. Says Loftness, “Any building that’s not designed around daylight has to be abandoned during a blackout,” like the blackouts that accompanied Hurricane Sandy. By contrast, daylit buildings can shelter occupants effectively during daylight hours and cut down on the need for emergency power.

At this solstice, and any time of year, daylighting has reemerged as a powerful trend in American architecture. Thank goodness. In these dark times, Loftness notes, “daylighting is nature’s gift to us all.”