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Model Lighting Ordinance

Model Lighting Ordinance. Based on System Performance By David M. Keith & Jefferey F. Knox. Model Lighting Ordinance. community measures to restrict the impact of outdoor lighting by and on neighbors

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Model Lighting Ordinance

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  1. Model Lighting Ordinance Based on System Performance By David M. Keith & Jefferey F. Knox

  2. Model Lighting Ordinance • community measures to restrict the impact of outdoor lighting by and on neighbors • goals include reducing glare, overlighting, energy use, light trespass or spill light, light pollution or skyglow and improving the visual environment • all of these goals should be measured by the performance of entire lighting systems

  3. Why “Based on System Performance”? • evaluate performance by the lighting system’s effect on neighbors • spill light, uniformity, uplight and for the most part glare metrics are only relevant for lighting systems • designs can (and will) vary -as long as the results are adequate

  4. What are Lighting Systems? • everything it takes to produce the desired luminous environment • Equipment: lamps, ballasts, photosensors, luminaires, poles, arms, foundations, wiring, controls, and ? • Energy: suitable electrical power, delivered to site, uninterrupted and paid for • Maintenance: repair and replace

  5. Measuring Impact of Lighting • evaluate any impacts of lighting at the property line • any restrictions are determined based on the classification or zoning of the property the light is landing on, not where it is coming from • put a box around the property and evaluate what tries to cross the boundary • no restrictions on equipment or installation

  6. Measuring Impact of Lighting • evaluate impacts using objective metrics • illuminance for “light trespass” or spill light • luminance for “glare” • use plan review and site measurement • account for substitutions, changes, errors • can restrict environmental impacts • unit power density for energy • unit uplight density for light pollution

  7. Measuring Impact: Illuminance • illuminance restrictions for limiting “light trespass” in the form of spill light • measured as both/either vertical and/or horizontal at the property line • semi-cylindrical would be better than vertical - disregard the azimuth element • hard to measure at present • limit of 1 to 10 lux depending on context

  8. Measuring Impact: Luminance • luminance restrictions for limiting “glare” • “glare” is excessive contrast • bright areas against dark background • outdoors at night, background can be “black” • a limit on luminance becomes a limit on glare • establish simple and measurable limits • “no more than 1000 cd/m2 in a 2 degree field” • measured with a standard calibrated meter

  9. Measuring Impact: Luminance • why “1000 cd/m2 in a 2 degree field”? • T12 fluorescent at 3200 lms, 4 ft by 1.5 inches • with 4pi steradians per sphere, for 3,200 lms, the spherical intensity is around 250 candela • with the projected area at 0.5 sqft (0.05 m2) “average” for T12 is 500 cd/ft2 (5,000 cd/m2) • compare with “cutoff” for 100W HPS • 0.10 * 9500 lms would be 950cd for 80-90 deg elev.

  10. Measuring Impact: Energy • if energy is a concern, use power allowances for the entire site • based on the size and zoning, perhaps areas • allow for flexibility and trade-offs • be sure allowance is adequate to meet recommended practice and a bit more • consider “incentives” - changes in allowance depending on controls or other factors

  11. Unit Power Density (UPD) • characteristic of entire lighting system • reflect trade-offs and evaluate options • corresponds to explicit and hidden costs, including pollution and energy use • already used in interior lighting • can easily be tailored to fit the community • “incentives” for controls - a self-imposed curfew or reduced lighting levels

  12. Measuring Impact: Light Pollution • if light pollution is a concern, establish a metric for uplight and include it in criteria • total uplight allowance for an entire site based on zoning, perhaps areas and tasks • a simple metric could combine all flux above horizontal - as installed over the entire site - with an assumed average reflectance (say 18% used in camera light meters) to establish a value • not really suitable for field measurements

  13. Unit Uplight Density (UUD) • relatively simple metric of lighting system’s “contribution to ambient light pollution” • relates to the performance of the system • evaluate trade-off between contributions from luminaire - distribution and aiming - and reflected light • must be adequate to meet recommended design practices

  14. MLO Based on Lighting Systems • limit on impacts by and on neighbors • evaluate the entire lighting system • objective metrics, at the property line • illuminance and luminance limits • can include energy and uplight restrictions • can be checked at plan submittal and (mostly) measured as actually installed

  15. Model Lighting Ordinance Based on System Performance By David M. Keith & Jefferey F. Knox

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