The effect of street and area lighting on the illumination of building façades and light trespass

Outdoor lighting fixtures are used to illuminate surrounding streets, parking lots, walkways, and the landscape surrounding many buildings. Examples of these light fixtures are cobra head streetlights, Acorns and Colonials. These streetlights are typically designed to achieve illumination levels required by published design standards such as minimum illuminance levels on parking as well as pedestrian walkways. The light from poles close to buildings often spills off onto building façades. This influences the illumination of the façade and impacts on light trespass ordinances of some municipalities. This paper develops a method for studying such an effect and outlines ways to minimize the effect of outdoor lighting on façade illumination without compromising parking lot and walkway illumination. A comparison is made between various types of area and road light fixtures.