22 August 2006
Figure 3-3. Examples of IESNA full cut-off luminaires.
LIGHT TRESPASS. Light trespass is referred to as nuisance glare or the
"light shining in my window" effect. It is usually caused by a glare source that is bright
compared to the darker night surround. Since glare inhibits our ability to "see" tasks
and decreases contrast, all designs must minimize glare.
Uncontrolled light sources (floodlights) are usually the cause of light trespass.
Not only does light trespass cause neighbor annoyance, but it also increases light
Figure 3-4. Glare results in loss of visibility.
3-8.1.1 To minimize light trespass, use only fully shielded or IESNA full cutoff
luminaires for area lighting. When unshielded luminaires such as wall packs and
decorative luminaires are used at low mounting heights, reduce the lamp brightness to
that of a 4200 lumen lamp (similar to a 55 watt induction lamp) or less. Do not overlight
areas because reflected light can also result in complaints and poor visibility by
increasing visual adaptation. Also, consider dimming or turning lighting off when not
needed and activate with motion sensors or timers when activity occurs.