Luminance of less than 2,500 cd/m2 between 45 and 90 degrees from nadir

Hi Henri, Even I would love to get enlightened on this matter, were you able to source some guidance or not yet?

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?

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.SPEC.pdf  No value can exceed 7000. The limit is NOT average luminance. It is not to exceed 7000 anywhere between 45 and 90

 

Sorry to jump on an older thread. I'm in the same situation. Customer says "use light fixtures with a luminance of less than 2,500 cd/m² between 45 and 90 degrees from nadir" which is outside of my understanding. I only have the basic Photoview IES software (I do have the ies files, a total of 8 files). Anyone here feel like helping me out for a starbucks gift card?  I'm not an engineer, but for the last 2.5 years I've been made responsible for IES/LM/TM files and it makes my brain hurt )

Rick,  I see that your post is a few months old, however, if your questions are not answered I can empathize (and hopefully offer a few insights).  I too, am not an engineer - and it took a lot of internet searching and talking to experts to wrap my head around this lighting requirement.  First thing - it is very important to understand that you are seeking the value in candelas per m2.  No other value is applicable.  There are very few manufacturers that are publishing this data on their cutsheets.  This is understandable, because the variations in models will affect the outcome (lenses, lumen power, etc.).  In the absence of data on the cutsheet you will need to run the IES file through a photometric tool (such as the "Visual Photometric Tool" that Maria mentions above).  You can access a free version through the LEED credit libaray.  The value in this program is termed "Luminance data, or Average Luminance".  Please note that there may be cases where you do not get the desired "chart" outcome - in that case, reach out to the manufacturer.   Once you have the "chart":

•  The horizontal headings are the "Horizontal veiewing angle" (imagine you are looking up at a fixture in open space and walking around it.  You start at 0 degrees, walk 1/4 of the way around it (that is 90 degees), halfway is 180 degrees) and so on.  Note that the values often (only) range from 0 to 90 because the fixture is wholly symmetrical and the values are the same in each quadrant.
• The first column represents the "vertical angle" from Nadir.  The (horizontal) values in the table associated with the vertical angles between 45 and 90 may not exceed the (cd/m2) limit.  Note that in v4 this limit is 2500 cd/m2.  In v4.1 this limit is 7000 cd/m2.  (this is why most of us will choose to pursue this credit under v4.1 criteria provided the necessary fixtures also meet the v4.1 criteria (example: minimum of 90 CRI).  

These are the basics - hope this helps.   

Rick, First off you want to use the LEED 4.1 version of the credit which you can do on 4.0 projects. It’s overall easier to use and get points. And the 2500 limit in 4.0 is a mistake that never got corrected. Limit in 4.1 is 7000.  You need a IES photometric viewer that will generate the calculated luminance table. We use photometric  toolbox but that is paid software. There may be a free viewer out there that does this. I don’t know.