855773520-LEED-v5-ID-C-Reference-Guide-Launch-Edition-1 - Page 338
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PATH 2. QUALITY ELECTRIC LIGHTING
Properly focused lighting at the right level and quality enhances concentration and minimizes distractions. Poorly lit spaces can cause headaches and eye discomfort, while well-illuminated work environments can help reduce stress levels and improve the overall well-being of employees. Electric lighting glare can significantly impact specific populations, such as aging adults and neurodivergent individuals, by causing discomfort, visual strain, and even emotional or cognitive disruptions. [136 ]
Projects must meet both Electric Glare Control and Color Rendering requirements within all regularly occupied spaces. Exceptions to the electric glare requirements include wall-wash fixtures properly aimed at walls, as specified by manufacturer’s data, indirect uplighting fixtures, provided there is no view down into these uplights from a regularly occupied space above, and 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 glare control can be documented based on individual luminaire specifications (luminance) or for the space as a whole unified glare rating (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. [137] Luminance information for the luminaire can be found in manufacturer specifications or on IES photometric plan files.
Unified glare rating (UGR) 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 [138] .
Color rendering: color rendering index (CRI) 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
136 Aryani, S., Kusumawanto, A., Suryabrata, J. & Wijaya, D. (2024, March), The correlation of lighting and mood in the workplace: digital image-based research, https://www.researchgate.net/publication/378820577_The_correlation_of_lighting_and_mood_in_the_workplace_digital_image- based_research. 137 WELL Standard v2, https://www.v2.wellcertified.com/en/wellv2/light/feature/4. 138 NEMA White Pater on Unified Glare, https://www.nema.org/standards/view/white-paper-on-unified-glare-rating-(ugr)
U.S. Green Building Council LEED v5 Reference Guide for Interior Design and Construction, April 2025 Launch Edition 327