Controlling Light Pollution
We should all be aware of light pollution when designing an outdoor lighting system. What is it?
Light pollution is artificial light that is obtrusive, excessive, and misdirected. Excessive light
pollution can result in disrupted ecosystems, interference with astronomical research, and wasted
There are three main types of light pollution: sky-glow, glare, and light trespass.
· Sky-glow is the glow effect seen over any large city.
o It is the combination of unshielded upward directional light and reflected light.
o An example would be poorly-executed architectural lighting, which was not
properly locked into adjustment.
· Glare is light from an unshielded light source.
o This can be very unsafe —glare can limit a person’s vision.
o For instance, a flood light controlled by a motion sensor that is facing directly
toward oncoming traffic from a driveway will create glare.
▪ A driver could be distracted with light projecting in their eyes, causing
obstructed vision and a potential accident.
▪ Attaching a shield or simply adjusting the fixture can solve this safety hazard.
· Light trespass is light that accidentally (or purposely) intrudes from one property to another.
o This tresspass happens frequently in landscape lighting.
o Often, misdirected wall wash, down lighting from trees, and/or over-lamped up
lighting can spill over into neighboring properties.
o An old landscape lighting design technique was to position ground-mounted
uplights from one property to illuminate the back sides of tall trees on another.
▪ This technique is still used today.
▪ We recommend that a contractor seek the permission of the neighboring
property owner before proceeding; written permission is always suggested.
▪ A specific switch for this technique is also advisable.
▪ A switch will control this bank of special effect lighting for evenings when
your client is entertaining.
▪ When done properly, this technique can allow all parties involved a very
In summary, light pollution can be controlled. Using the proper lamp or integrated fixture that is
shielded can significantly reduce glare. Proper aiming, Kelvin temperature, lenses, and louver
selection can also cut down on light pollution.
For more information on light pollution, visit www.globeatnight.org