Using daylight to illuminate commercial interiors is far from a new concept. Until the Industrial Revolution, daylight was the primary light source for buildings.
With the advent of electric lights in the 20th century, however, less emphasis was placed on natural light as a primary source of illumination. Windows became smaller and were sometimes eliminated completely. Energy-saving florescent lighting became commonplace and workers soon found themselves spending as much as 90 percent of their time away from natural light.
As a result, workers have experienced everything from eye strain and lack of energy to seasonal affective disorder and sick building syndrome. Until recently, the benefits of natural light were based largely on anecdotal evidence, but research studies conducted in the last couple of years now offer hard data that building owners cannot ignore.
Daylight not only makes commercial buildings more attractive to workers and customers, but also affects companies’ bottom lines through improved worker productivity, higher sales and reduced energy costs.
While the benefits of daylight are only recently gaining widespread acknowledgment and respect in the United States, the correlation between natural light and employee health has long been established in Europe.
Construction codes in many European nations dictate the maximum distance a worker can be from a natural light source, such as a window or skylight, and windowless offices are never permitted. Daylight is not considered to be a luxury for top-level executives with the coveted corner offices, but a basic human requirement for all workers.
– Building Design Affects Bottom Line
This level of commitment to natural lighting has not yet been realized in the United States, but more and more businesses are sharing their experiences with smart day-lighting strategies. The result is a growing body of evidence that using daylight can help businesses retain employees longer, provide a healthier and happier workplace, and stay more competitive through higher productivity and lower operating costs. Natural lighting and energy-efficient building design are also added bonuses for building owners looking to increase the value and marketability of an investment property.
Consider these statistics concerning energy savings:
According to the U.S. Department of Energy’s Energy Efficiency and Renewable Energy Clearinghouse, artificial lighting accounts for as much as 40 percent to 50 percent of the energy consumption in many commercial and institutional buildings.
According to the U.S. Green Building Council’s Sustainable Building Technical Manual, well-designed daylighting can reduce lighting energy use by 50 percent to 80 percent.
Lockheed Martin reported a 75 percent reduction in its electricity costs (approximately $500,000 annually) after daylighting its Sunnyvale facility.
According to a 1998 Harris poll, lighting is the number one contributor to worker productivity.
The U.S. Green Building Council’s Sustainable Building Technical Manual reports that worker productivity can be increased by up to 15 percent by implementing smart daylighting.
According to the Rocky Mountain Institute, productivity gains of 6 to 16 percent, including decreased absenteeism and improved quality of work, have been reported from energy-efficient building design. Since companies spend an average of 70 times as much money (per square foot per year) on employee salaries as on energy, an increase of just one percent in productivity can result in savings that exceed the company’s entire energy bill.
– Property Value and Marketability
Green projects typically sell or lease faster and retain tenants better because they combine superior amenity and comfort with lower operating costs and more competitive terms. The resulting gain in occupancies, rents and residuals all enhance financial returns.
According to the Electric Power Research Institute, daylit buildings can result in 10 to 20 percent higher rental income than those that use only artificial light.
Day-lit properties are likely to rent faster and for higher rates. Additionally, when the owner is ready to sell the building, the investment in energy efficiency should bring added resale value.
A 1999 Pacific Gas and Electric Co. day-lighting study analyzed a retail chain of 108 stores where two-thirds of the stores were lit with skylights and one-third were not. All other things being equal, the study found that the daylit stores had 40 percent higher sales than those without.
A 1995 Wall Street Journal article reported on Wal-Mart’s experience with its store in Lawrence, Kan. Sales were significantly higher in the portion of the store that utilized skylights than the same products displayed at other Wal-Mart stores.
To test the correlation, products were swapped from the artificially lit to the day-lit sections and those located under the skylights again had significantly higher sales, while those shifted to the artificial lights returned to their national sales average.
– Reduced Absenteeism
Pennsylvania Power & Light reported absenteeism dropped 25 percent after natural light was introduced to its work force.
A study by the U.S. Department of Energy found that employees exposed to natural light have 20 percent fewer symptoms common to workers in “sick buildings.”
According to the Center for Health Systems and Design at Texas A & M; University, providing patients with daylight aids in the healing process.
Studies show that patients are apt to recover faster and to handle the stress of being ill better in environments with plenty of natural light.
Smithsonian magazine reported mortality rates are lower in intensive care units that have natural light than those without.
The basic human connection to daylight is only beginning to come to light with these new research findings. As we move further into a new century of innovation and discovery, sophisticated day-lighting tools will continue to change the way we light commercial interiors.
Digert is technical director of Solatube International Inc.
