2. INTRODUCTION
There
is an increasing concern for the problems
created by unwanted light at night.
Lighting designers are faced with conflicting
challenges
Meeting Local ordinances controlling the light
Meeting the needs of having the light
3. PROBLEMS
Light
Trespass
Also known as “obstructive light”, defined as
unwanted light that falls beyond the property line or
area intended to be illuminated.
Results of light trespass
Spill Light. Lighting areas beyond the area intended to be lit.
Producing illuminance outside of the property lines.
Brightness. Bright sources within the observer’s field of view,
such as direct viewing of luminaires.
Discomfort glare
Disability glare – Reduction in the visibility of significant
visual tasks
4. PROBLEMS
Who does light trespass having the largest negative
impact on?
Neighborhood residents
Unwanted light shining into homes at night
Desire to have a low level of ambient light
Drivers
Disability glare can seriously affect a driver’s visibility
and ability to locate and recognize signal lights.
5. PROBLEMS
Biggest Offenders
Street lights with inadequate optical control
Sports field lighting
Commercial lighting
Biggest Reasons
Excessive and unnecessary use of lamps with light lumen
output
Incandescent floodlights improperly aimed
Luminaires left on all dusk to dawn for no real purpose
6. PROBLEMS
Light
Pollution
Also known as “sky glow”, defined as light that is
directed upward to the sky or reflected from surfaces
that is interference.
Results of light pollution
Natural and manmade particles in the air scatter light rays
from outdoor lighting and create an artificial fog in the sky.
General Public
Astronomy
7. PROBLEMS
Even light from well-designed lighting systems will
reflect from objects being illuminated and light will
enter the atmosphere. Almost impossible to
eliminate all light from entering the atmosphere.
9. SOLUTIONS
Luminaires that allow for control of light above the
horizontal plane.
Semi-cut-off
Cut-off
Full cut-off
Luminaire shields
Reduce amount of light on highly reflective
surfaces.
Review lighting systems
10. LEED
Light Pollution Reduction Credit
Must provide cut sheets of all luminaires along with a
plan showing horizontal and vertical footcandles.
Projects attaining this credit saw an average of
30% electricity savings due to elimination of
luminaires and reduction in lumens.