To minimize light trespass from the building and site, reduce sky-glow to increase night sky access, improve nighttime visibility through glare reduction and reduce development impact from lighting on nocturnal environments.
Project teams must comply with the interior lighting requirement AND 1 of the 3 options for exterior lighting.
For interior lighting
All nonemergency built-in luminaires with a direct line of sight to any openings in the envelope (translucent or transparent, wall or ceiling) must be automatically controlled to turn off during all after-hours periods during the performance period. The total duration of all programmed after-hours periods annually must equal or exceed 2,190 hours per year (50% of annual nighttime hours). Manual override capability may be provided for occasional after-hours use.
Implement a program to ensure that the lighting control system is being properly used to adjust lighting levels during all after-hours periods.
For exterior lighting
If the project is certified under LEED for Schools or New Construction, show that SS Credit 8: Light Pollution Reduction was earned. If the project is certified under LEED for Core & Shell Development and 75% of the floor area is LEED for Commercial Interiors, show that SS Credit 8: Light Pollution Reduction was earned for both systems.
Partially1 or fully shield2 all exterior fixtures 50 watts and over so that they do not directly emit light to the night sky.
Measure the night illumination levels at regularly spaced points around the perimeter of the property, taking the measurements with the building’s exterior and site lights both on and off. The building’s interior lights must be in the same state during both measurements. At least 8 measurements are required at a maximum spacing of 100 feet apart (30 meters), so as to be representative of the illumination levels at the perimeter of the property. The illumination level measured with the lights on must not be more than 20% above the level measured with the lights off. This requirement must be met for each measurement point; averaging of all points is prohibited.
2 To be LZ4, the area must be so designated by an organizations with local jurisdiction, such as the local zoning authority.
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