Taking Exterior Illumination to Task
Finding quality design in outdoor lighting has often been a challenge, but a growing recognition of exterior environments is bringing a change in this trend. The standard lighting fixtures around buildings rate-for the most part-poorly when it comes to light pollution, trespass and illlumination quality.
Finding quality design in outdoor lighting has often been a challenge, but a growing recognition of exterior environments is bringing a change in this trend. The standard lighting fixtures around buildings rate-for the most part-poorly when it comes to light pollution, trespass and illlumination quality. And poor exterior lighting is also being recognized as an energy-efficiency issue, with the understanding that wasted light is wasted energy use as well. According to numbers from the International Dark-Sky Association in Tucson, Ariz.-a membership-based nonprofit group dedicated to controlling light pollution-there is an estimated $1 billion in wasted outdoor-lighting electricity every year.
As these issues have begun to impact professionals designing outdoor environments, a number of lighting, government and even astronomy organizations have begun making an attempt to address them. At the heart of these attempts are new codes and recommended practices for lighting designers.
Pollution and trespass
Light pollution -light that is unnecessarily thrown straight up into the atmosphere-from outdoor fixtures initially became an issue among astronomers when light intruded on their ability to view the skies at night. It has also become a symptom of urban sprawl, as the spread of a city casts its light to surrounding areas. Similarly, light trespass -light that is thrown outside of the area intended to be illuminated, such as onto neighboring houses or businesses-is an issue that is worst in large cities.
Around buildings, the biggest culprits of pollution and trespass are the fixtures found in security, display and parking-lot lighting. The most commonly prescribed remedy is specifying fully shielded , or full-cutoff , fixtures for all exterior illumination. These fixtures direct light down and to the sides by blocking or reflecting it. In order to be classified as a fully shielded fixture, no light can be thrown above a horizontal line through the fixture. Many manufacturers now produce such fixtures for outdoor applications, or can even provide shields to be retrofitted onto current fixtures.
Other large producers of light pollution and trespass are sports parks or fields, with the required lighting levels reaching up to 300 foot-candles in some of the most prominent professional venues. In addition to the pollution and trespass issues, poor lighting design-that shoots light all over rather than concentrating it onto the players and fans-can often increase glare, which in the end makes it more difficult to play and watch the game.
Glare is a facet of illumination quality , an area where a great deal of current outdoor lighting does not rate well. Lighting on and around buildings is quite often guilty of trying to illuminate a large area with one large lighting source, which not only contributes to pollution, but also compromises light quality. Floodlights that spread light over a large area often cause a great deal of glare and shadow, which can actually be counterproductive in security applications.
With the amount of wasted outdoor lighting, choosing the most cost-effective lamp can be an important way of improving energy efficiency . In many security and parking-lot applications, low-pressure sodium fixtures -which offer poor color rendering but excellent energy efficiency-will actually be sufficient.
Controlling the times that fixtures are on is another way of cutting energy usage. Lighting control in the form of timers and photosensors has become standard practice in outdoor lighting applications and should always be used to limit unnecessary lighting. Another energy-saving control is the motion sensor , which can turn on the lights only when a person is present.
By specifying the correct lamp, directing it only toward its outdoor application and seeing that it only shines when necessary, lighting designers can help protect the outdoor environment while improving the quality of illumination and saving energy.