One early productivity study measured the effect of lighting on the productivity of factory workers. Because this factory’s name was the Hawthorne Works, the productivity improvements are known as the Hawthorne Effect. More recent studies have shown that natural light is most effective for improving employees’ productivity, whether the employees work in a factory or in an office.

Natural light produces different colors than artificial light. Although employees can still see under artificial light, their bodies may respond differently. According to the University of California, Davis, studies suggest that a human needs natural light to properly calibrate his body’s circadian cycle. If this cycle is off balance, workers may become fatigued or stressed because their sleep schedule does not match their work schedule.

Some studies suggest that natural light is more important during winter. The sun is much weaker in the far north during the winter, and it is up in the sky for less time, so a worker will not be exposed to much sun outside of standard work hours. This can lead to seasonal depression. Placing workers in sunlight during winter did get them to focus more on their work, according to a Rochester Polytechnic Institute study.

Natural light does not just improve the performance of employees. Providing natural light helps students pay attention in school, so the students perform better on achievement tests. Using natural light in a retail store improves customers’ mood, so the store sells more products.

Because employees don’t feel as good under artificial light, they may unconsciously take more breaks so that they can stand outside underneath the sun. When employees are exposed to the sun during work, they take fewer breaks.

The design of a new building can incorporate daylight, but many companies can’t afford to build a new building. As an alternative, some companies have installed daylight guidance systems. A daylight guidance system uses mirrors, tubes, or fiber optics to direct light from outside the building to offices inside the building which are far from the building’s windows. According to the University of Rochester, a daylight harvesting system usually costs about $600 to install, and improves productivity by 5.5 percent on average.