The lighting for urban exterior areas and buildings must be “community-responsive,” The design must be accepted by the residents, neighbors and the community. The IESNA recommends the following steps in the design process:
Examine the community’s architectural theme to help establish a local identity. Examples are “entertainment and excitement”, or “stately, quiet and intimate.”
Determine local and community lighting ordinances. These are standards that address light pollution, light trespass, min./max. illuminance levels, and which will affect the lighting design.
Identify the surrounding brightness. These surrounds are classified as dark, medium and bright. Parks and residential neighborhoods are examples of dark surrounds. Bright surrounds are downtown metropolitan areas and industrial parks.
Identify the neighboring areas and calculate the luminance of adjacent roadways, walkways and properties. This will help define luminance ratios that are suitable to the activity taking place in the area being lighted. A ration of 1:2 will allow the lighted area to blend in with the surround. A ratio of 1:10 will result in the lighted area being highly accented. However, exceeding a 1:10 ratio may cause distraction for motorists just as floodlighting a residential property at that ratio would result in complaints from the neighbors.
The lighting design must also be “energy-responsive”.
Save energy by choosing the highest efficacy lamps and ballasts like SYLVANIA METALARC® POWERBALL® Ceramic Metal Halide lamps and precisely matched QUICKTRONIC® MH Series electronic HID ballasts.
Select luminaires and lamps that place the light only where it is needed and at the right illuminance levels, to further reduce energy consumption.
Introduce lighting control systems when appropriate. Illumination levels can be reduced or lighting systems can be selectively or completely shut off during unoccupied or late night periods to save even more energy and observe local lighting ordinances.
One needs only fly over a US city at night to witness this firsthand. In our effort to light our roads and allow nighttime use of facilities, light pollution has become a major consideration when designing outdoor lighting. Stray or reflected light is emitted and scattered by dust water vapor and pollutants into the atmosphere causing the sky to glow above urban areas.
Street and area lighting luminaires, including those used for sports venues and parking lots should be specified that minimize or “cut off” direct upward light emission. These will not eliminate all emission above the horizontal plane due to the reflective characteristics of the ground or pavement.
Luminaires that project light upwards on architectural facades, signage and landscape features should have distribution characteristics or accessory devices that minimize light outside the target area.
Much of our non-critical exterior lighting can be turned off during post midnight hours. The installation of lighting controls and motion sensors allows safety and security lighting to be shut off or operated at lower levels when areas are unoccupied.
Light Trespass can be as simple as a streetlight shining through a bedroom window. Most often it is defined as excessive brightness in the normal field of vision, also called “nuisance glare.” While many local ordinances and laws have been written to control it, enforcement is difficult. Light trespass ordinances that limit horizontal illumination are sometimes ineffective since vertical illumination can also be the cause. For example, extremely bright objects on a dark field can be an annoyance even though there is no horizontal illuminance involved.
Identify any areas adjacent to those being lighted that might be sensitive to light trespass, for example residences, roadways and airfields.
Specify luminaires that have optical and light distribution features designed to contain the light output inside the design area. Use the same guidelines for location, mounting height and aiming angles of luminaires
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