At the Greenbuild conference in November 2013, the U.S. Green Building Council (USGBC) released the fourth generation of the Leadership in Energy and Environmental Design (LEED) green building rating system. LEED v4 represents a major update, including notable changes affecting lighting design and selection.
The USGBC will allow projects to register for either 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, and hospitality and healthcare facilities.
Of particular interest is a new lighting quality provision worth 1 point. EQc6, Interior Lighting (1 point) lists eight options and requires adoption of at least four of them in the design:
LEED v4’s lighting intent is to reduce direct glare, achieve good color rendering, place light on walls and ceilings for visual comfort, ensure useful light is reflected rather than absorbed by room surfaces, and to produce balanced brightness (luminance, though USGBC here uses the term “illuminance,” which refers to light level measured in foot-candles).
These requirements may impose a premium but otherwise need not be burdensome; it involves selecting carefully shielded luminaires with good color rendering, long-life light sources and a majority providing some uplight. Suitable solutions are widely available. High-reflectance work surfaces will raise light levels and brighten walls and ceilings, while managing luminance ratios will promote visual comfort.
If occupants can adjust the lighting to satisfy task needs and individual preferences, the designer can also gain a second point (EcQ6, Interior Lighting). This would involve enabling 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. Bilevel switching and manual continuous or step dimming would qualify. The same flexibility must be provided in multioccupant spaces. In addition, presentation lighting must have a separation control, and the control must be in the same space and offer a direct view of the controlled lighting.
If the lighting is controllable from a central point, it may be able to support participation in a demand response program (EAc4, Demand Response, 1 point) or at least enable participation (1 point). Advanced lighting control systems providing metering capability can support achieving EAc3, Advanced Energy Metering (1 point). All lighting and controls must be commissioned (EAp1), with 3–4 points for enhanced commissioning (EAc1, which could include monitoring), with activities such as developing a systems narrative, schedule of light levels throughout the building, runtime schedules, functional testing, systems manual, and operator and occupant training.
Meanwhile, requirements to achieve the light pollution point (SSc6) are more sophisticated, based on the IES backlight/uplight/glare (BUG) luminaire rating system. And achieving energy points (EAp2 and EAc2, up to 18 points) is now much tougher, based on the 2010 rather than the 2007 version of the ASHRAE/IES 90.1 energy standard. Note the standard’s Table 9.6.2 lists lighting controls that may be used to save energy beyond code if the control credits are claimed as savings rather than additional interior lighting power when using the Space by Space Method and energy modeling.
Overall, LEED is getting more challenging to beat from an energy point of view, enhancing the risk of designers prioritizing points over lighting quality. The new lighting quality point recognizes the importance of ensuring the lighting system does what it’s supposed to do, with the requirements being readily achievable using best practice.
Check out the new LEED v4 at www.usgbc.org/credits.