Integrated Daylighting Systems

GPG-015, July 2014

As a component of integrated lighting systems, daylight harvesting offers the opportunity to reduce lighting energy consumption by using natural light to offset electric light in perimeter workspaces. GSA’s GPG program assessed the performance of daylight harvesting at five federal building sites, and found an average annual energy savings of 27% and simple payback as low as four years. Click on the infographic below to enlarge.

GPG Findings 015, July 2014, Integrated Daylighting Systems. Opportunity: How much energy is used for lighting in U.S. commercial buildings? 26% of electricity goes to lighting. Lights often on even in sunlit areas. Technology: How do Integrated Daylighting Systems save energy? Available natural light offsets use of electric light. Effective where perimeter depth is two times the maximum window height. Measurement and Verification. Where did M and V occur? Lawrence Berkeley National Laboratory measured IDS performance at 5 federal buildings to evaluate incremental savings from daylight harvesting. Results: How did Integrated Daylighting perform in M and V? 27% average savings 0.84 kWh/ft2. Best practices: unobstructed sky views, limited seasonal variation, window-to-wall ratio 0.5, visible transmittance of 60%. Less than 6 years payback with high occupancy. Deployment: Where does M and V recommend deploying Integrated Daylighting? Sites with high lighting use. New construction and retrofits with existing lighting power density greater than 1.1 W/ft2 and energy intensity greater than 3.3 kWh/ft2. Results are for fluorescent lamps, LED lamps have different performance characteristics.

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Last Reviewed 2017-03-29