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By Faith Baum & Elizabeth Johnson
Illumination Arts had the privilege of being selected as a Subject Matter Lead for the LEED v4 Reference Guides, working with a team assembled by our colleagues at YR&G. Participating in this process has given our team a unique perspective on the development and intent of the lighting-related LEED credits.
Changes to the LEED Rating System include new categories, shifts in point distribution and streamlined organization of related categories. While LEED requirements have always sought to reduce energy usage and ensure occupant comfort, version 4.0 shifts focus from limiting the environmental impact of lighting to increasing the positive contributions that lighting can bring to a project.
Some of the lighting-related credits have become simpler to document while others have become more challenging. Over the coming year, our bi-monthly Light Notes newsletter will include a discussion of each of the categories that are affected by lighting. This month, we are focusing on Indoor Environmental Quality – Interior Lighting, which applies to both buildings and interiors.
INDOOR
ENVIRONMENTAL QUALITY
EQ
CREDIT INTERIOR LIGHTING
The Interior Lighting credit is intended to promote occupant productivity and comfort while providing high quality lighting. It applies to New Construction, Schools, Hospitality, Data Centers, Warehouses and Distribution Centers. Retail and Healthcare projects can also use this credit with modified requirements. Two possible points are available and either one or both can be pursued.
The Lighting Control option, worth 1 point, is similar to the requirements in LEED v.3.
• 90% of individual occupant spaces need individual lighting controls with at least three light levels or scenes (on, off, midlevel).
• 100% of multi-occupant spaces must have
- Multizone control systems with at least 3 light levels or scenes.
- Separately controlled lighting for presentation or projection walls.
- Controls located in the same space as the luminaires they control.
The Lighting Quality option, worth 1 point, requires at least four of the following eight strategies be met.
Light Fixture and Source Based Strategies (A-D)
A. For all regularly occupied spaces luminaires must have less than 2,500 cd/m2 between 45-90° above nadir. (Except wallwashers, indirect/direct luminaires not visible from above and adjustable fixtures.)
B. The CRI for all light sources must be greater than 80 except for color changing and specialty sources.
C. 75% of the total connected load must have a rated life of at least 24,000 hours or L70 for LED.
D. Only 25% or less of the total connected load in regularly occupied spaces can be directly-only lighting.
Strategies A and D are about minimizing direct glare. The higher color rendering required by Strategy B is directly related to the quality and appearance of the space. Long life sources ensure that the design intent is maintained and the opportunity for lamp replacement errors is limited.
Surface and Material Reflectance and Illuminance Based Strategies (E-H)
E. For 90% of the regularly occupied floor area, the area-weighted average surface reflectance must be at least 85% for ceilings, 60% for walls and 25% for floors.
F. For furniture within scope the area, the weighted average finish reflectance must be at least 45% for work surfaces and 60% for walls.
G. For 75% of the regularly occupied floor area the ratio of average wall surface illuminance (not including fenestration) to average work plane illuminance must not exceed 1:10. Must meet one of the previous reflectance requirements (E or F) or walls must have a minimum area weighted average reflectance of 60%.
H. For 75% of the regularly occupied floor area, the ratio of average ceiling surface illuminance (not including fenestration) to average work plane illuminance must not exceed 1:10. Must meet one of the previous reflectance requirements (E or F) or ceilings must have a minimum area weighted average reflectance of 85%.
The combination of high reflectance finishes with indirect illumination reduces contrast between the room surfaces and the work plane, improving visual acuity and occupant comfort. Choosing four of these options to pursue early in the project design process makes it easier to design a lighting system and select finishes to meet these requirements.
