Hi all!
I need clarification regarding mean lamp lumens for light pollution reduction credit. Most specification sheets of light fixtures only show the initial lumens value, not mean lamp lumens. At one of our project sites, LED exterior light fixtures were used, and the specification sheet only shows the initial lumens value. After discussing this with a lighting vendor, I learned that LED lamps may retain around 90% or more of their initial lumens over their rated life. Based on this information, the Lighting Maintenance Factor (LMF) is considered to be 0.90.
Mean lamp lumens can be calculated as:
Mean lamp lumens = Initial lamp lumens * LMF
Can I use this formula to find the mean lamp lumens value?
If the mean lamp lumens value exceeds 2500, we need to shield the light fixtures. To prove compliance, can I submit the technical specification sheet of the light fixtures that shows the details regarding the shielding, along with site photographs?
Bill Swanson
Sr. Electrical EngineerIntegrated Design Solutions
LEEDuser Expert
734 thumbs up
April 19, 2024 - 8:54 am
mean lamp lumens = Average lamp lumens over the lamp's rated life.
LEDs are considered end of life at .70 output. The curve is a bit convex. Most people use a LMF of 0.90 for LED. Worst case is 0.85.
You should be safe using that formula