What Is Residual Lighting?

Interior Sources

• The most common form of residual lighting in interior applications is digital clocks, power indicators and illuminated screens on appliances and computer equipment. Each of these casts a glow that illuminates the insides of homes and offices.

Exterior Sources

• Exterior sources of residual light come from street lights, security lights, landscaping lights, billboards and other signage. These sources of extra light added together create what is called an "urban glow" around today's cities.

Scientific Ramifications

• Polysomnographers, scientists who study sleeping habits, have found that interior residual lighting affects people's ability to achieve a good night's sleep. Exterior residual lighting has made it difficult for astronomers to study the stars, as urban sky glow and glare increase and visibility decreases. New lighting designs and requirements are focusing on minimizing residual lighting.