Daylighting Systems: Improving Productivity and Happiness?

According to the U.S. Department of Energy, daylighting* is defined as the use of windows and skylights to reduce the need for artificial lighting during daylight hours... without causing incremental heating or cooling problems.

Daylighting Definition:

The Whole Building Design Guide describes daylighting as "the science of not just how to provide enough daylight to an occupied space, but how to do so without any undesirable side effects.

"Beyond adding windows or skylights to a space, it involves carefully balancing heat gain and loss, glare control, and variations in daylight availability.

For example, successful daylighting designs will carefully consider the use of shading devices to reduce glare and excess contrast in the workspace. Additionally, window size and spacing, glass selection, the reflectance of interior finishes, and the location of any interior partitions must all be evaluated.

"A daylighting system consists of systems, technologies, and architecture. While not all of these components are required for every daylighting system or design, one or more of the following are typically present:

• Daylight-optimized building footprint
• Climate-responsive window-to-wall area ratio
• High-performance glazing
• Daylighting-optimized fenestration design
• Skylights (passive or active)
• Tubular daylight devices
• Daylight redirection devices
• Solar shading devices
• Daylight-responsive electric lighting controls
• Daylight-optimized interior design (such as furniture design, space planning, and room surface finishes)"

Daylighting Considerations Include:

• South-facing windows that allow most winter sunlight into a structure, while limiting direct sun during the summer, therefore avoiding over heating of the building.
• North-facing windows that admit relatively even, natural light, while producing little glare, delivering almost no unwanted summer heat gain.
• East- and West-facing windows that provide good daylight penetration in the morning and evening, respectively, but may cause glare, admitting a lot of heat during the summer when it is usually not wanted, and contributing little to solar heating during the winter.
• Daylighting is important, not only for energy savings, but also to limit eyestrain. Eyestrain by electric lighting has not been shown to cause long-term health effects, but the symptoms can be debilitating while they last, reducing worker productivity. Eyestrain can lead to irritation of the eyes, inflammation of the eyes and lids, breakdown of vision- blurring or double vision, headaches, indigestion, etc. can be caused by electric lighting. Eyestrain can be caused by inadequate light for a given task, excessive contrast between different elements, and flickering of lights (even when the flicker is not visible).

While daylighting can eliminate eyestrain, provides more light on a task than electric lighting, and reduces excess contrasts from shading, it is still important to provide occupants with control over window blinds for the highest level of productivity.

Circadian Stimulation

Although it's difficult to believe, building and interior designers in the 1960s believed that windowless schools and office buildings illuminated solely by fluorescent lights minimized distractions, prevented eyestrain, and created greater efficiency in heating and cooling. This lack of natural light in many schools may have had a negative effect on learning.

Environmental biologists theorize that windows that admit daylight and provide ample and pleasant views can dramatically affect mental alertness, productivity, and psychological well-being.

Contact with natural daylight promotes circadian stimulation, regulating physical and mental function through our natural responses to the rhythms of light.

Circadian dysfunction can even cause cardiovascular problems, immune dysfunction, cognitive and functional deterioration, and depression. Also, exposure to full spectrum sunlight enables the synthesis of vitamin D which promotes nerve and muscle function, as well as cell growth regulation.

Exposure to daylight has been linked to better production of melatonin, controlling sleep cycles, which allows people to achieve higher levels of concentration and better short-term memory recall. Suffice it to say that exposure to daylight has better outcomes for worker performance.

While daylight and electrically generated lighting may seem comparable, the productivity levels associated with exposure to the two different kinds of lights are disparate. For happy and productive workers, go with large south-facing windows with occupant control capability!

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* The term daylighting is not to be confused with an alternative definition of the term daylighting (aka "potholing") that is the practice of exposing buried services and/or facilities, such as pipes and conduit, which provides visual confirmation of the condition of buried lines.

* Photo credit by Jeremy Levine via Flickr