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Fenestration Forum: August 2012

Daylighting dimensions, part 1

August 20, 2012  By Brian Burton

Most readers will already know that designing and installing effective
daylighting systems for buildings is not only an art but a very complex
science as well.

Most readers will already know that designing and installing effective daylighting systems for buildings is not only an art but a very complex science as well. Natural illumination practices are changing the fenestration industry at a very rapid pace and will likely continue to do so for the foreseeable future. The evolution in the way we make provision for lighting in buildings has not entirely kept pace with the changes in our workplace and home environments, so we are now playing catch-up. We have fallen behind to a certain degree because most lighting designs for buildings in the past were tailored to enable traditional tasks to be completed on a desk – horizontal viewing. Today, most tasks in the workplace are completed using computers – vertical viewing.

Daylighting is defined as controlled admission and interplay of direct sunlight and/or diffused skylighting within buildings to assist in creating a productive, healthy and visually stimulating indoor environment in an economically beneficial manner. Fenestration apertures such as windows, skylights and solar tubes allow natural light to penetrate deeper into the interior of buildings. When combined with responsive or automated lighting control systems, they can also significantly reduce the demand for electrical power for heating, cooling and artificial illumination.

The impact of fenestration components and the natural illumination they can provide on occupant productivity and psychology is much greater than the average citizen realizes. We often take for granted the benefits of natural illumination in buildings and the components that provide building occupants a view of the exterior. According to Boris Lamontagne, a researcher at the National Research Council of Canada and an adjunct professor at Carleton University, who is currently developing a novel type of switchable glass, “We expect to be able to see the outdoors when we are in a building and if occupants are denied a view of the exterior for an extended period, the negative impact on their sense of well-being can affect the occupant’s concentration skills, reaction times and efficiency.”We are obviously unable to function effectively without light because we are dependent on adequate illumination for our perception and motor skills. But it is also not surprising that lighting plays a large part in our psychology, health and overall productivity. Whether it be outside or inside, we have always placed a tremendous value on natural light because it provides us with a sense of time and a vital connection that is needed by our internal biological clock. Most of us spend over 90 per cent our time indoors. It is no wonder that illumination, whether it be natural or artificial, is a valuable commodity.


From a historical perspective, the topic was not studied scientifically until the late 19th century; however, over the last 20 years scientists and illumination engineers have learned a great deal about the topic and there is no doubt that it is very complex. Formal studies in the field of photobiology, conducted in schools, universities, hospitals and office environments, have proven without a doubt that natural daylighting in buildings produces significant benefits. Designers also discovered that daylighting requires careful balancing of a number of factors and special considerations. For example, in modern offices where workers are now often viewing computer screens, it has become apparent that the issue of avoiding glare and other visual discomforts has to be taken into consideration.

Designers have also recognized certain limitations that include variations in available light due to the time of day, weather conditions, seasonal variations and a number of other factors. Because each building is unique, no single illumination design approach will suit every structure.

When buildings are properly designed, daylighting not only provides psychological benefits and productivity improvements, it also saves energy. Electric lighting accounts for between 35 and 50 per cent of the total electrical consumption in commercial buildings. Electric lighting also increases the loads on mechanical cooling equipment, adding additional costs.

Although daylighting is not intrinsically superior to artificial light, when accomplished with appropriate controls, it is generally considered superior to artificial illumination, less expensive and as having less of an impact on the environment.

Brian Burton is the author of Building Science Forum and is serving on CSA’s Fenestration Installation Technician Certification Committee. Brian is a research and development specialist for Exp (The new identity of Trow Associates). He can be contacted at or through

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