Forum discussion
Strategy A states: "For all regularly occupied spaces, use light fxtures with a luminance of less than 2,500 cd/m2 between 45 and 90 degrees from nadir."
Referring to the luminance tables on cut sheets/.ies files, to determine the luminance of the luminaire, should you add the luminance values for each horizontal angle together, take the maximum of all the values, or take the average of all the values to compare to the 2,500 cd/m2?
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Kera Lagios
High Performance SpecialistEHDD
16 thumbs up
July 22, 2016 - 7:11 pm
We did further research into this issue, contacting lighting professionals who were involved in developing the credit. They told us that for Strategy A, the maximum luminance value for the angles between 45 and 90, inclusive, should be used.
Lauren Sparandara
Sustainability ManagerGoogle
LEEDuser Expert
997 thumbs up
April 13, 2017 - 11:19 pm
Thanks for following up and sharing this information, Kera.
Erica Baranik
Sustainability ConsultantStantec
2 thumbs up
May 3, 2017 - 12:33 pm
I have a follow-up question to the one above, provided to me by our project's Lighting Design Lead:
Should the measurement be “Zonal lumens” and not “candelas/sm”? Zonal lumens are published as a standard piece of information in a photometric report. They are reported referenced to the angle from nadir. Candelas per sm are an output result if you create a calculation using a photometric report and are reported in a flat plane not in angles from nadir. Could you provide some guidance on what the desired measurement is?
Maria Peralta
Energy Consultant - LEED AP BD+CECOPENTA
3 thumbs up
November 8, 2017 - 2:07 pm
Erica Baranik,
We are working on a project and the same doubt has arisen as you. I see that in this chat you have not received any answer to your question, but have you managed to resolve the doubt in any way?
Thank you very much
Kera Lagios
High Performance SpecialistEHDD
16 thumbs up
November 8, 2017 - 9:16 pm
Hi Erica,
Hopefully I can help out a bit. First, to answer your question about metrics, the correct unit is cd/sqm. That is becuase the characteristic in question is luminance, not illuminance. Abstracted a bit, luminance is a measure of "brightness", which is what this strategy is trying to evaluate.
In order to find it if it's not on the cut sheet you would need a program similar to Photometric Toolbox. In that program you can load the .ies file and it will provide various metrics. One of these is the Luminance Data table. This table shows data from 45 to 85 degrees in 10 degree steps. If any number in that table is greater than 2500 cd/sqm, then the fixture does not comply.
So far, we have not found a direct only fixture that meets this criteria. If anyone does find one, let the forum know!
The best way around this is to use direct/indirect lighting or indirect only lighting. It's a little unclear in the LEED Guide, but even a fixture with a direct component will be exempt if it has an indirect component (and it is not possible to see into the indirect component from above).
I hope that helps!
Kera
Pedro Julio Silva Perez
MrDINPRO SA
December 6, 2017 - 7:15 pm
Hello Kera,
Reading your last post, I want to ask to you if the average luminance in the following dropbox file, meet the A. strategy requiment.
https://www.dropbox.com/s/qawv0pnrvy03xh5/HBLED-LD5-24SE-N-UNV-L850-ED2-...
how do I read the average luminance table? is The nadir data in the purple or green higlighted column data?
Thank you for your attention.
Pedro
Kera Lagios
High Performance SpecialistEHDD
16 thumbs up
December 7, 2017 - 1:06 pm
Hello Pedro,
Nadir is represented by the "0" row. That is the angle pointing straight down (if, for example, you are using a downlight). LEED looks for at the values from 45 to 85 inclusive - in other words you can ignore the top row, but not the other rows. The file you sent does not meet the requirement because all of the numbers in columns 0, and some of the numbers in columns 10, 20, 25, and 35 have values greater than 2500 cd/m2. As we understand it, to meet the requirement, all of the number, except for that top row, must be lower than 2500cd/m2. We have yet to find any downlights (incremental or linear) that meet the requirement. If you find one, please post!
JAMES CHEN
Delta ElectronicsJuly 18, 2018 - 11:16 pm
Hi, Kera
I see that above post about" The best way around this is to use direct/indirect lighting or indirect only lighting. It's a little unclear in the LEED Guide, but even a fixture with a direct component will be exempt if it has an indirect component (and it is not possible to see into the indirect component from above)."
It mean is use indirect lighting will be exempt the strategy A states, or maybe measure light fixtures with a luminance of less than 2,500 cd/m2, but do not need to be limited by 45 degrees to 90 degrees.
Which one is correct?
Thanks
Ricardo Sá
Director of SustainabilityEdifícios Saudáveis Consultores (503 910 767)
85 thumbs up
November 22, 2018 - 11:15 am
Hi,
Common IES photometric files have distribution diagrams and candela tables. Both allow us to read candelas in each direction and checking maximum for 45º-90º. Nonetheless, I am having trouble analysing this information and checking compliance with LEED requirement (2500 cd/m2).
How do I take the candelas information to get cd/m2 for a specific luminaire? Which area it referes to?
Can you help?
Ricardo
Maria Porter
Sustainability specialistSkanska Sweden
271 thumbs up
June 7, 2019 - 8:47 am
Ricardo, I don't know if this helps. I had the same problem, but determined to crack this nut (not being a lighting specialist), I went into the settings menu in the photometric tool and ticked all the boxes, and then the cd/m2 appeared!
/Maria
Kevin Bolger
August 29, 2019 - 11:14 am
I guess this is a somewhat old post but I wanted to know if you are able to find downlight fixtures that meet this requirement regularly now days, seems like there area a lot based on cut sheets I have been getting? I am still trying to figure out how to get the luminance data from an IES file when the cutsheet does not include it. We use AGi at my office and it doesn't seem to be able to provide this information, just the LCS and BUG data.
Chris Lopez
September 3, 2019 - 1:49 pm
Hello Kera,
In regards to one of your earlier posts, when reading the luminance data table, from 45 to 85 degrees, Am I correct when I read that, while excluding the first row of numbers, that the all of the other readings need to be less than 2500 cd/sqm for the fixture to comply? or is it just the column for 45-85 that needs to read under 2500 cd/sqm?
Chris Lopez
September 3, 2019 - 6:50 pm
Hello Kera,
I just wanted to clarify reading the luminance data table. As you state, asides from the top rows of values, if the value is anything about 2500 cd/sqm, than the fixture does not comply.
Catalyst Partners
Catalyst Partners7 thumbs up
September 30, 2019 - 5:10 pm
Pedro, could you share the dropbox link again or send me a screen shot of the cut sheet that Kera looked over?