How windows affect occupants’ well-being

Windows provide critical exposure to the natural environment
Monday, December 16, 2013
By Barbara Carss

Researchers are theorizing that the universal appeal of sunshine and scenic views out of windows is more than just an aesthetic preference for building occupants. Rather, it’s an intrinsic need for a species that now spends most of its time indoors, in contrast to its evolutionary history.

Recent work at the National Research Council‘s (NRC) Institute for Research in Construction builds on earlier findings about visually and non-visually triggered impacts of exposure to light and natural vistas. This offers an added, and sometimes conflicting, dimension to more established approaches to building design and performance.

Code drafters have traditionally viewed windows as a source of ventilation and potential means of emergency egress, while green building and energy efficiency advocates increasingly focus on thermal loads and daylight harvesting opportunities. The emerging third direction of investigation explores links to occupants’ health and behaviour.

“A space with a window is viewed as being more pleasant than a space without a window. You don’t know need someone from the National Research Council to tell you that,” Guy Newsham, group leader with NRC’s Intelligent Building Operations, informed seminar attendees this December at the PM Expo in Toronto. “A lot of these things are common sense. They are things we already know, but what’s the science behind that?”

A 1984 comparison of two groups of patients recovering from surgery is one the first studies to demonstrate positive outcomes attributed to a view. Patients with sightlines to a natural setting recovered more quickly and required less pain medication than those looking out to a neighbouring brick wall. Subsequent studies have found links between a view of nature and improved blood pressure, heart rates, emotional moods and ability to concentrate.

One theory attributes these outcomes to the restorative exercise of leisurely inspecting natural settings, which offers a break from acute concentration while also reinvigorating the brain for renewed concentration. Biophilia — the theory that humans have an instinctive bond to other living systems — looks farther back in time.

“That’s a theory that we are attracted to environments that are much more like the environment in which we evolved,” Newsham noted.

The same theory comes into play with humans’ requirement for light. Indoor light is typically at a level of about 400 lux, which refers to the measure of light intensity and the spread of illuminance over a given area. In comparison, outdoor light ranges from 10,000 to 100,000 lux.

“If you follow evolutionary theory, it would suggest that our bodies are designed to experience conditions outdoors,” Newsham said. “The general population does not receive very high light levels (indoors). We are constantly exposed to dusk.”

Exposure to daylight is important for non-visual receptors linked to the release of the hormone melatonin, which regulates sleep and other regular body cycles. Scientists’ discovery of these receptors — known as intrinsically photoreceptive retina ganglion cells — in 2001 has spurred new research into the signals that human bodies receive from the environment. In turn, this has raised new considerations for building design, operations and healthy practices for building occupants.

Workers located near a window may fare somewhat better than those ensconced in cubicles more centrally in the building’s floor plate, since light levels at the perimeter tend to be at about 1,000 lux. However, proximity to a window may have negative aspects, such as glare, excess heat or cold, and acoustical issues.

“Big windows lead to big glare issues,” Newsham observed. “Unwanted bright light is sort of the light equivalent to noise.”

This is also where conflict can occur with other building functions and design features. Already there may be tradeoffs between heightened thermal loads and potential for savings through daylight harvesting, and human behaviour adds an extra element of uncertainty. Notably, once blinds are closed, they tend to remain that way.

“The energy issues are very complex. When people close blinds, it will destroy any light saving. You are probably losing about half of your (theoretical) light energy savings when you put blinds there,” Newsham said. “Maybe it’s better to have a small window that’s always (got its blinds) open than a bigger window that’s always covered.”

On the flipside of chronic underexposure to daylight, most urban dwellers are overexposed to light at night. In response, the International Commission on Illumination sets out principles for healthy lighting and associated lighting hygiene tips.

Timing of exposure particularly affects non-visual receptors, which are most sensitive to light in the blue-green range of the spectrum, so people are advised to seek sunlight during the day and to avoid electronic screens later in the evening and within 30 to 60 minutes before bedtime. Bedrooms should be as dark as possible for sleeping. Global lighting is recommended rather than solely using desktop task lighting, and blinds should be reopened as the sun moves and glare abates.

Finally, people are encouraged to engage in productivity enhancing activities.

“Give yourself permission to stare out windows,” Newsham advised.

Barbara Carss is editor-in-chief of Canadian Property Management and Building Strategies & Sustainability magazines.

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