855773644-LEED-v5-BD-C-Reference-Guide-Launch-Edition - Page 510

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any other specific applications (i.e., adjustable fixtures). Exceptions to the color rendering requirements include non-white light sources used for decorative color effects that are in addition to the general illumination.

Electric light glare control can be documented based on individual luminaire specifications (luminance) or for the space as a whole (UGR).

Luminance

Minimizing light fixture luminance helps reduce disability and discomfort glare. The threshold, 6,000 candela per square meter (cd/sq. m.) between 45 and 90 degrees from nadir, was selected to align with WELL v2 Feature L04 — Electric Light Glare Control . [179] Luminance information for the luminaire can be found in manufacturer specifications.

Unified Glare Rating

Unified Glare Rating (UGR) is a measure of the discomfort produced by a lighting system along a psychometric scale of discomfort. The value of 19 corresponds to just acceptable glare. The UGR approach requires software modeling calculations of the designed lighting. Modeling must be performed as outlined in the NEMA White Paper on Unified Glare Rating [180] .

Color Rendering: Color Rendering Index

Color Rendering Index (CRI) is the most widely adopted method for evaluating color fidelity. The CRI requirement of 90 or above indicates that the light source closely mimics natural light, allowing colors to appear vibrant and true to their actual hue. This is especially important in environments where color differentiation is critical, such as in medical facilities, retail spaces, or galleries. CRI information for the luminaire can be found in manufacturer specifications. The luminaire must have a CRI of at least 90.

Color Rendering: TM-30-20

TM-30 is a newer method developed by the Illuminating Engineering Society (IES) for measuring color fidelity. The luminaire requirements for this credit are based on the Priority Level 1 criteria for the Preference design intent recommendation in TM-30-20 Annex E (see Table 8). This threshold was selected to align with WELL v2 Feature L08 – Electric Light Quality . [181]

179 “Electric Light Glare Control”, WELL Standard v2, (n.d.) https://v2.wellcertified.com/en/wellv2/light/feature/4. 180 “NEMA White Paper on Unified Glare Rating”, NEMA, (2021), accessed March 21, 2025, https://www.nema.org/standards/view/white-paper-on-unified-glare-rating-(ugr) 181 WELL Standard v2, https://v2.wellcertified.com/en/wellv2/light/feature/8.

U.S. Green Building Council LEED v5 Reference Guide for Building Design and Construction, April 2025 Launch Edition 500