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	Fixed and movable features such as vertical blinds shown above can block and reflect direct sunlight entering through windows.

“Once you demonstrate that daylighting makes all those things happen, clients are much more willing to sit down and listen to what you have to say.”

Artificial lighting accounts for as much as 40-50 percent of the energy consumption in most commercial and institutional buildings, and 10-20 percent of energy consumption in industry, says the U.S. Department of Energy. Daylighting can significantly reduce those costs, says the DOE.

Daylighting, once confined to museums, boutiques and architectural oddities, is, today, an increasingly integral element of contemporary design. Daylighting, as part of an integrated design, results in energy savings and increased performance by building occupants.

Despite the potential benefits of daylighting, only a tiny fraction is captured in buildings today.

“Many architects are knowledgeable about the benefits of daylighting design, but many are still in the dark (pun intended),” says Jeff Rutledge, head of the skylight division of a major U.S. curtain wall and skylight system manufacturer and installer.

Daylighting and the impact of daylighting strategies on the lighting, heating and cooling of buildings is, perhaps, the most intriguing, and the most vital, construction issue facing building owners and design professionals.

	Chicago Police Headquarters, Chicago, IL To make the most efficient use of glazing systems, designers of Chicago Police Headquarters added a shading device, which is supported by the curtain wall system.

Daylighting and Productivity
Ongoing research into daylighting as a source of energy conservation is voluminous. The subject of daylighting became common currency, however, when the Heschong Mahone Group’s now three-year-old study on daylighting and productivity caused such a cultural stir that results were reported by 50 newspapers. Author Lisa Heschong was surprised to find herself on National Public Radio and the CBS News.

The two-pronged Heschong-Mahone study concluded, in short, that daylighting, the effective combination of exterior glazing, skylights and control systems, greatly improved student performance in schools and boosted retail sales.

The report studied the correlation between daylight availability and human productivity. The study was done in two parts. One looked at the test scores of 20,000 elementary students in three school districts and concluded that daylight in classrooms resulted in a more than 20 percent improvement in test scores. A second part of the study looked at retail sales. Its conclusions: sales were as much as 40 percent higher in stores with skylighting.

In June 1993, Wal-Mart opened a new store in Lawrence, Kan., that became the prototype for a majority of the new Wal-Mart stores that followed—all of them daylighted.

A foray into sustainable architecture, designed by Tulsa-based BSW Architects, in consultation with William McDonough Architects, the Center for Resource Management and the Rocky Mountain Institute and The Weidt Group, the Lawrence store was designed for energy efficiency. It had a glass arch at the entrance for daylighting, an efficient lighting system, an HVAC system that utilized ice-storage and special light-monitoring skylights developed specifically for the project.

As a cost-cutting measure, Wal-Mart decided to install skylights on only half the roof, leaving the other half without daylighting. Because each of Wal-Mart’s cash registers is connected in real time headquarters in Bentonville Ark., it was soon apparent, says Tom Seay, vice president of real estate, that “sales pressure was significantly higher for those departments located in the daylit half of the store.” Sales also were higher than for the same departments in other stores.

“We are daylighting the large majority of our projects now,” says Bill Correll, Wal-Mart director of architecture.

Often, as the Heschong-Mahone study notes, daylighting may not even be apparent to those in the building. Interviews with shoppers done as part of the firm’s 1999 survey asked the question: “What do you think of the skylights in this building?”

“The typical response was to look up, look puzzled, and then say, ‘That’s funny, I never noticed them before.’” Out of 42 interviews in 10 skylit stores, Heschong says, only three shoppers were aware of the skylights.

“The questioner then asked: ‘Does this store feel any different to you than other stores like this?’ By far the most common response (80 percent) was ‘This store feels cleaner.’ The second most common response (65 percent): It feels more spacious, more open.’”