GREEN buildings are healthy buildings that promote a sense of well being and high productivity. Building occupants enjoy thermal, acoustic and visual comfort in green buildings. Among these benefits, people are quite familiar with what thermal comfort is. They are likely to react to heat or cold by natural or mechanical means to achieve comfort levels. People are instantly aware of the discomfort brought about by noise, especially intrusive noise.

Unfortunately this is not the case with visual comfort which is the least understood by many people. Many are slow to accept that some of their physical ailments are attributed to the absence of visual comfort in their environment.

For example, did you know that poor lighting can cause headaches and eyestrain causing people to be irritable thereby causing poor productivity? Poor lighting can also lead to concentration problems, so critical for students and workers alike.

Daylighting, visual comfort

Visual comfort is brought about by having good lighting which is adequate both in quality and quantity. The source of light may either be natural or artificial or a combination of both. In any case, windows have distinct advantages.

Today there are still many new buildings that do not fully utilize the benefits derived from using natural light.

Efficient daylighting considers heat gain, glare, different light levels, uniformity and solar penetration.

The three basic rules of good daylighting are: 1) avoid direct sunlight on heavy viewing tasks to prevent glare; 2) let natural light in through skylights and good-sized windows that give deeper penetration and better distribution; and, 3) filter daylight and bounce it off surrounding surfaces with the use of vegetation, curtains, sunscreens and shades.

When locating buildings in a particular site, correct spacing together with proper orientation must be maintained to enhance natural lighting.

Natural lighting

Adequate window openings must be maintained to ensure that building interiors get enough natural lighting.

In the early ?60s it was fashionable for many buildings and homes to have blank, windowless façades to underscore the architectural trend sweeping the world then. Some of these structures are still existing. One can just imagine the visual discomfort suffered by their occupants, not to mention the energy they waste through the use of additional artificial lighting and mechanical ventilation systems.

To get proper distribution of daylight, designers should strive to have some sky visible from most places inside the building.

While it may not always be possible, rooms should have visual access to the outdoor environment.

In countries with little sunlight, they resort to daylighting with mirrors designed and installed outside the building that direct sunlight to where it is needed inside the building.

Natural light may come direct along a straight path from the sun. It may also come as diffused light from the sky. Externally reflected light from the ground or other buildings bring light. Internally reflected light also comes from inner walls, ceilings or other surfaces.

Glare is caused by strong contrasts in light levels or high levels of light. Bright light reflected off light-colored surrounding causes glare. Glare may be mildly distracting or even visually blinding. It may also be caused directly or indirectly.

We need to light spaces with artificial lighting after dark. Some spaces need artificial lighting even during the day. In this case the spectrum of artificial light should be as close as possible to natural light. Lighting requirements depend on specific occupants and activities.

Very important

Distribution of light is very important. Visual comfort depends on the amount of difference between daylight levels beside windows and at a difference from them. Too much contrast and high level of illumination cause discomfort to the eyes. Therefore natural and artificial lighting should meet health requirements in intensity, brightness, protection against glare and avoidance of shadows.

Lighting takes up around 20 percent of the electricity bill in homes, 30 percent in commercial spaces.

Bright light must not be in workers? field of view. Blinds, louvers and shutters help keep off glare. Room illumination should not be too high in comparison with computer display screens. Computer displays with dark background do not hurt the eyes at 18-46 foot candles luminance, the measure of light given by a candle at a distance of one foot, equivalent to watts per square foot. Higher light levels are acceptable for white background screen.

Work surfaces and reading corners should be lit as directly as possible. The rule of thumb is every table should have its own direct light.

Flexible and dimmable lights are very helpful for different lighting requirements in the same areas. They also bring down energy use and carbon emissions.

Summer is here. It is time to wear visors and hats to protect our eyes when out in the sun.

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