The U.S. Green Building Council recently released the fourth generation of the Leadership in Energy & Environmental Design (LEED) green building rating system. Projects can register for LEED 2009 or LEED v4 until June 1, 2015, after which LEED v4 will be required. The new LEED covers new construction, commercial interiors and existing buildings, with specific requirements for schools, retail, data centers, warehouse and distribution centers, hospitality and healthcare facilities.
LEED v4 represents a major update, including notable changes impacting design and selection of lighting.
Notably, LEED now encourages “lighting quality” in a new provision, EQc6, Interior Lighting (1 point). EQc6 lists eight options, shown below, and requires adoption of at least four of them in the design:
A. selection of luminaires with limited brightness (<2,500 candelas per square meter) between 45 and 90 degrees from nadir (straight down), with some exceptions; B. use of light sources with a color rendering index (CRI) of 80+, with some exceptions including site lighting and colored lighting, intended to provide good color rendering for the application; C. use of light sources in at least 75 percent of the connected lighting load that have a rated life of at least 24,000 hours; D. use of direct-only overhead lighting for 25 percent or less of the connected lighting load in all regularly occupied areas; E. in at least 90 percent of the regularly occupied floor area, at least 85 percent reflectance for ceilings, 60 percent for walls and 25 percent for floors; F. similar threshold of 45 percent reflectance for work surfaces and 50 percent for movable partitions in areas with work furniture; G. in at least 75 percent of the regularly occupied floor area, meet a ratio of average wall surface brightness to average workplane brightness that does not exceed 1:10 (must also meet option E, F or achieve area-weighted 60 percent reflectance for walls); and H. in at least 75 percent of the regularly occupied floor area, meet a ratio of average ceiling surface brightness to average workplane brightness that does not exceed 1:10 (must also meet option E, F or achieve area-weighted 85 percent reflectance for ceilings). Satisfying these requirements involves choosing carefully shielded luminaires and long-life lamps with good color rendering, with a majority of luminaires providing some uplight. High-reflectance surfaces can raise light levels and brighten walls and ceilings. Managing brightness ratios promotes visual comfort (photometric brightness as in luminance, though USGBC here uses the term illuminance, which refers to light level measured in footcandles). If the lighting is adjustable by occupants to satisfy task needs and individual preferences, a second point may be gained (EcQ6, Interior Lighting). This involves giving occupants a choice of at least one level of light output between 30 and 70 percent of full output in at least 90 percent (new construction, commercial interiors) or 50 percent (existing buildings) of regularly occupied spaces. Appropriate control strategies include bilevel switching and manual continuous or step dimming. The same flexibility must be provided in multioccupant spaces, and presentation lighting must have a separation control, with this control located in the same space as and offer a direct view of the controlled lighting. A wide range of other lighting controls are required in LEED, including daylight harvesting and bilevel lighting, as LEED v4 is based on satisfying the ASHRAE/IES 90.1-2010 energy standard, not the 2007 version, as a prerequisite. This, combined with more restrictive interior lighting power allowances in ASHRAE/IES 90.1-2010, makes achieving energy points (EAp2 and EAc2, up to 18 points) much tougher with lighting. Note the standard’s Table 9.6.2 lists lighting controls that may be used to save energy beyond the standard if the control credits are claimed as savings rather than additional interior lighting power when using the Space by Space Method and energy modeling. More on that here.
If the lighting is controllable from a central point, lighting may be able to support participation in a demand response program (EAc4, Demand Response, one point) or at least enable participation (one point). Advanced lighting control systems providing metering capability can support achieving EAc3, Advanced Energy Metering (one point).
All lighting and controls must be commissioned (EAp1), with 3-4 points for enhanced commissioning (EAc1, which could include monitoring), with activities including developing a systems narrative, schedule of light levels throughout the building, runtime schedules, functional testing, systems manual and operator and occupant training.
For outdoor lighting, the light pollution (SSc6, 1 point) requirements are more sophisticated, based on the IES Backlight/Uplight/Glare (BUG) luminaire rating system.
Overall, LEED v4 is more restrictive and sophisticated regarding lighting, demanding creative design solutions, detailed and layered control strategies, and commissioning. While LEED has become even more challenging, greater sophistication will increase demand for the services of design professionals who can satisfy its requirements.
Check out the new LEED v4 at www.usgbc.org/credits.