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NC-v4 EQc6:Interior lighting

Option 2 Lighting Quality- Part E - LRV

Hello,

We are pursuing strategy E for lighting quality. We received a carpet spec which includes two LRVs: 

LRV – L value: 50.4

LRV - Y value: 18.8 

If I am not wrong, L value is reflectance under fluorescent light and Y value is reflectance under natural light. Which value should we use for credit calculations?

Thank you,

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Kera Lagios
High Performance Specialist
EHDD
LEEDuser Basic Member
16 thumbs up

Mon, 02/05/2018 - 04:35

Hello, LEED is interested in reflectance values of surfaces. In general, reflectance (also called "light reflectance values" in some cases) is a way to characterize how much a particular color is capable of reflecting light regardless of the source that it is under. The values LRV-L and LRV-Y do not have anything to do with the source that is shown upon them. Luminance, which is defined as the apparent brightness of a surface, depends partly on the amount of light hitting the surface (regardless of whether the source), but also the reflectance or LRV of the surface. Looking into your particular example, you list "LRV - L" and "LRV Y". I believe these are combining (3) separate terms: LRV, L*, and Y*. 
  • LRV, Light Reflectance Value, is defined by the British Standard 8493.
  • L* is color depth, as defined by the CIE L*a*b* color space. Is NOT equivalent to reflectance, but is used to calculate LRV. L* is much higher than LRV, and should not be used as a reflectance value. 
  • Y* is luminance as defined in the CIE xyY color space (which is somewhat confusing given the definition of "luminance" I gave above - the Y* value, however is different). 
Simple answer: LRV-Y is the value you should use for LEED.  More information (admittedly, none of it from published or reference sources): I found this information on a reliable lighting software site and used it to check your example as well. They show a term "rho(p)" is roughly equal to LRV: rho(p) = 100 x ((L+16)/116)^3 If we use your value of LRV-L for "L": rho(p) = 100 x((50.4+16)/116)^3 rho(p) = 18.75 A few other potentially useful sources: http://thelandofcolor.com/world-authority-lrv-light-reflectance-value/ https://en.wikipedia.org/wiki/CIE_1931_color_space Best, Kera
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LEEDuser Basic Member
1 thumbs up

Tue, 02/27/2018 - 00:33

Hi Kera, Good to connect with you here. I have a follow-up question: is LRV on carpets a new qualification? I have researched and talked to reps about carpets, particularly about their LRV values. So far, no luck. Do you know of any manufacturers or products that may have LRV data associated with them? Thanks, Juta

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