Forum discussion
Hello, i'm new into the LEED requirements.
My customer ask me if we have light fixtures with a luminance of less than 2,500 cd/m2 between 45 and 90 degrees from nadir.
Is there some guideline how I can calculate this?
My feeling is this somehow has to do with glare, but I can't get my head around this is measured in cd/m2 and there is no distance to a surface involved. Is this a property of a luminaire that can be listed in a spec sheet, or is this the result to be measured in a lightplan?
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Priscilla Joseph
3 thumbs up
December 6, 2022 - 6:53 am
Hi Henri,
Even I would love to get enlightened on this matter, were you able to source some guidance or not yet?
Maria Porter
Sustainability specialistSkanska Sweden
268 thumbs up
December 6, 2022 - 7:17 am
I just want to say first that I am no lighting expert. But I have managed to figure out how retrieve the data. First save the LDT or IES file for the lamp. Often on the website of the producer. Then open "Visual Photometric Tool", same as referred to in the "Light Pollution" credit. “Unpack” the file in the program, make sure to check “Average Luminance” under “Settings”. Then you will find some kind of table with “Cd/m2”. Almost always the numbers are way to high for credit compliance. But for one supplier they weren’t. The rivaling company said that the first one had the wrong numbers. And none of them knew how the test lab had put the numbers into their file, so it remains unclear if they are correct or not. It seem hard to get the credit in Europe, anyone have other experiences? Also, I don’t understand why output data is sometimes one dimensional (x-axis) and sometimes two dimensional (x- and y-axis table), what axis do I use then?
Owner of this page might have some insight for us all?
Henri Barten
Service ManagerOpple Lighting
1 thumbs up
December 6, 2022 - 7:22 am
It seems you do not always have to comply with all requirements, and with this particular requirement is about a certain group that is about Interior lighting quality. To earn a point under this Pilot Credit, you have to choose at least 4 out of the 8 features called Stategies. Strategy A states: "For all regularly occupied spaces, use light fixtures with a luminance of less than 2,500 cd/m2 between 45 and 90 degrees from nadir." and can be used when you want a warm low light and cosy room. The 2500 cd/m2 can only be achieved with indirect lighting, and nobody picks Strategy A, unless you want to use indirect lighting otherwise you will be sitting in the dark.
Glenn Heinmiller
PrincipalLam Partners
96 thumbs up
December 6, 2022 - 11:25 am
The 2500 cdm2 is LEED 4.0 is a mistake that was never corrected by USGBC. It's pretty much impossible to meet. Therefore this strategy (of the 8) is effectively not available in 4.0.
I always suggest that you use the 4.1 version for credit. You can get the luminance data with an .ies photometric viewer. Sometimes it is on the spec sheet. If you look on pages 5-7 of this spec sheet you will see the table on the right side of the page
https://www.axislighting.com/application/files/8916/6993/1370/BBR-LED-B3...
No value can exceed 7000. The limit is NOT average luminance. It is not to exceed 7000 anywhere between 45 and 90