Rating System

LEED BD+C: New Construction, LEED BD+C: Core and Shell, LEED BD+C: Schools

Rating System Version

v3 - LEED 2009, v2 - Schools 2007, v2 - LEED 2.2, v2 - LEED 2.0

Inquiry

The project is a four-story, 60,000 SF, speculative office building that is being submitted under LEED-CS. As we understand the intent, Credit SS8 - Light Pollution Reduction, aims to reduce light pollution through the control of interior lighting, exterior light distribution, and exterior lighting power density. Our question concerns the calculation requirements for the exterior lighting power density. We have been very diligent about reducing the overall lighting power density across the site. The site lighting has a 47% reduction of light power density as compared with the allowable light power density in ASHRAE 90.1.2004. All of our exterior site lighting is on a photocell/master time control system that turns off all non-emergency lights at 10pm. Because of the neighboring uses, we have voluntarily eliminated all building façade lighting on the western façade, which accounts for nearly a third of the total building façade. This allows us to focus our façade lighting on the public face of the building, adjacent to walkways, parking, etc.. Based on our total façade area (including the western façade) our lighting power density meets the credit requirement of 0.1 watts/SF. ASHRAE, however, calculates the LPD for each illuminated façade. Using this methodology, our LPD is 0.16 watts/SF, which is a 20% reduction from the ASHRAE standard. Does this meet the intent of the credit?