Scientists and doctors are increasingly interested in natural lighting benefits...
Benefits Overview -- Daylighting our Buildings
-- Bion D. Howard, B.E.S.T.

The scientific and medical communities are getting increasingly interested in the benefits of natural lighting in our buildings. There are documented benefits under increasing study including improvements to health, vision and mood -- not to mention the decrease in electric power used for lighting and the avoided air-conditioning loads of particular interest in commercial buildings.
Letting natural sunlight into our buildings has been shown to provide:

• Lessened severity of clinical depressionImprovement of our moods and attitude
• Boosts in test scores by school children
• Increased productivity of office workers
• The image of larger spaces indoors
• Better actual color rendering (colors "true to the eye")
• Reduced eyestrain in the workplace
• Lessened energy waste from electric lighting

More Cost Effective?

Tubular skylights can be more cost effective than either adding windows for light (not including "passive solar heating design"). Here is a comparison.

Tubular Skylights -- cost to install one unit is in the range of $300 to $600 depending on supplier (Daylite Co. has some of the most reasonable prices in North America). They provide light equivalent to and often of superior quality to regular lighting fixtures. A tubular skylight unit can be placed into nearly any type of indoor space, and may be mounted on almost any type of roofing system and pitch (roof incline). They have built in privacy since the optical glass faces skyward, and the diffuser unit is comprised of highly translucent facets not clear glazing.

Traditional Skylights -- cost to install one unit is in the range of $ 850 to $2,000 (or up for fancy custom units). The traditional skylight needs to have an elaborate framing project to erect the "bay" into which it is fitted. These bays also need additional insulation materials, and may require beefing up other attic or roof/ceiling framing to accommodate added load (weight or skylight and framing lumber). Years of experience show skylights will require maintenance and that rainwater leakage is a very common consumer call-back complaint. In most cases installing a skylight means the room below need to have a ceiling or attic space directly connecting to outdoors.

New Windows -- cost to install one unit (based on a typical window retrofit to a home) is in the range of $600 to $1,200 and will vary significantly by the type of sash specified. Wood windows can be many times more pricy than Vinyl windows. The installation of a window requires an outdoor wall, and considerable re-framing to create a new "rough-opening" for the window. This construction can be very messy and disruptive to family life. Once installed, a window also needs shades, curtains or draperies at added costs, to control privacy and lighting to the room. Window installations also require the home owner to get a building permit and may cause problems with a historic home, or with home-owners associations eager to control the "look" of a given community.

The Solution -- Daylighting !
Bringing natural light indoors can be made easy. There are a number of options, including adding windows and installing skylights, these may be more expensive from both installation and "hassle-factor" standpoints, not to mention their increased energy waste compared to smaller more efficient tubular skylights. A tubular skylight captures direct and ambient light, providing excellent illumination even on cloudy days and in early morning and late afternoon when the sun is low in the sky.

Since people often spend over 80% of the day indoors adding natural light to indoor spaces is key to improving productivity and health, show to be the case in numerous studies.

Lighting and Our Health is Amazingly Intertwined!
A large study, published in 1992 (Biological Psychiatry Journal), on using natural light to treat clinical depression was developed by a Veterans Administration physician, Dr. Kripke. He provided light treatments to 25 depressed patients at a VA hospital. Results indicated the patients who received natural white light became much less depressed than those got only artificial light.

Numerous people suffer from seasonal mood changes during the winter months and about 9 percent of our population suffer from "SAD" -- a condition called seasonal affective disorder. The SAD-condition makes people feel more tired, gloomy, and can lead to reduced appetite, poor sleeping habits and feelings of depression. Medicine has shown the most effective treatment for SAD is exposure to "natural" spectral lighting. However, the studies of SAD affected people indicate that it is likely to be the shorter time between sunrise and sundown that triggers SAD, rather than fewer sunny days in Winter.

Some SAD suffers have purchased expensive light boxes that use powerful full spectrum electric lamps to help beat back the symptoms. For about the same amount of money they could install a tubular Daylite System in their home, then use that space as a retreat to improve their outlook through basking in more natural light.

Productivity and Health
There are no standards or codes, yet, for levels of workplace natural illumination in the US. However in Europe there have been such standards for many years, in the building codes. In northern latitude nations (Netherlands, Sweden, Germany) there are code provisions indicating such things as the distance a worker can be located away from a window, and how much of a building's total lighting intensity should be coming from natural sources (i.e. sunlight).

The green building trend in the US is placing a new emphasis on natural daylighting systems in buildings, with commercial office spaces leading the way. There are as yet few guidelines for residential daylighting other than recommendations that all rooms be provided with a source of natural light to reduce potential electric energy waste during the day.

Several reports in the building science literature indicate productivity can increase significantly in day-lighted buildings, and absentee rates decline as well in the range of 15% to 50% less "sick time."

This independent briefing paper was prepared by:
Mr. Bion D. Howard, President
Building Environmental Science & Technology
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