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Light pollution

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Planning an efficient lighting system
     
Today, there exists a vast choice in luminaires that have been designed to reduce both energy consumption and light pollution.  To fully benefit from the newest technologies, however, a radical change in everyday habits is required.  This begins with conscientious planning of lighting systems so that they will economize light, energy and money.


1. Assess your requirements

Night lighting fulfills the dual needs of seeing and being seen.  This is the first question you should ask yourself:  Is lighting really needed? If so, then go on to define your requirements:

 
What?

What areas or objects should be illuminated?  Is complete lighting necessary or could a line of visual markers suffice?

 
 
It is useless to illuminate the rear of a building if it is not visited at night.


     
Completely uniform lighting of an area is not always necessary.  In some cases, it is possible to manage the night environment by placing a line of luminaires as visual markers to orient travelers.
 
How much?

How much illuminance is needed? The illuminance required mostly depends on ambient lighting levels. Remember that the eye does not adapt instantly to variations in illuminance and that a bright light in a dark background actually reduces visibility. A luminaire in a weakly lighted environment thus has a much greater effect than one in a strongly illuminated place.

 
When?

When is the lighting necessary? Artificial lighting often only creates a feeling of security, while not effectively increasing safety. This has been clearly shown in France, where extinction of roadway luminaires has led to a reduction in highway accidents.

By scheduling illumination for only certain hours of the evening, one can make use of timers to automatically switch off luminaires when not required.

 
2. Direct light where it is needed

Remember that only certain areas need to be illuminated. Concentrate lighting in these places only. Following this simple principle has several positive consequences. It:

  1. saves energy;
  2. decreases light pollution;
  3. reduces light trespass;
  4. increases safety.

Several luminaires offer an excellent control of luminous flux. Casting light upwards to the sky or onto adjacent areas is a waste of energy. If we were to think of luminaires as taps and leaking light rays as drops of water, we would never tolerate such an extravagance!

 
 
Source: Lumec


A luminaire that emits a concentrated beam of light offers better visibility than one that shines light in all directions.  In certain cases, the effects of glare can compromise safety.
 
Source: Lumec
 
3. Avoid glare

Glare occurs when the eyes are exposed to a relatively bright source of light compared to background lighting levels, which results in contraction of the pupils.  Visual perception is greatest when illumination is uniform and so contrasting glare significantly reduces visual performance and visibility.  Avoid producing glare by noting levels of ambient lighting and carefully controlling how beams of light are directed.

 


4. Plan your lighting system according to pre-defined needs

Once you have defined your lighting requirements, you are ready to plan your lighting system.

  • First, assess the environmental lighting level (roadway luminaires, signs etc.) to see how it could help fulfill your needs.
  • Next, find the best locations for installing luminaires.
  • Choose luminaires according to their photometric report.
  • Determine the minimum bulb strengths required, taking into account the surface area to be illuminated and the number, type, height and location of luminaires to be used.

You can check your lighting plan using point-by-point illuminance calculations. These values are generally available from manufacturers, distributors, engineers and architects. Also, feel free to use the examples of typical lighting situations as inspirations!