Whether or not one agrees with the specifics of the rating system, it is hard to dispute the role LEED has played in raising awareness about sustainable design. As interest has developed, designers in all building fields have moved to understand how these design criteria affect their respective disciplines. Over the past six years, as newer iterations of the system have been implemented, there have been more opportunities to incorporate lighting elements into the rating system. Let's consider how the role of lighting is changing among the LEED systems.

LEED Rating Systems

Currently there are four LEED rating systems that address commercial construction: LEED-NC 2.1 (New Construction); LEED-EB (Existing Buildings); LEED-CI (Commercial Interiors); and LEED-CS (Core & Shell). The U.S. Green Building Council, the organization behind the development of the LEED program, calls these systems 'products.'

LEED 1.0 was released in 2000. As of November 2002, LEED-NC 2.1 is the current rating system in place for new construction and renovation; however, a draft version of LEED-NC 2.2 was issued for public comment in December 2004. In addition to the LEED-NC products, LEED-EB was released in October 2004. LEED-CI was released in November 2004 for certification of commercial interiors, and applies to interior tenant improvements of new or existing office space. The intent is that it complements LEED-CS, which addresses core and shell construction. LEED-CS was released as a draft version in September 2003, and has not been finalized to date.

Performance Categories

Of all the 64 potential credits in the current LEED-NC 2.1 rating system, Credit 8, 'Light Pollution Reduction,' in the Sustainable Sites category, is the only one that relies solely on lighting. There are three main components to this credit. First, to limit light levels by meeting or providing lower light levels and uniformities than the IESNA Recommended Practice; Lighting for Exterior Environments (RP-33-99); second, to reduce skyglow by requiring luminaires with a lumen output greater than 3500 to be full cutoff; and lastly, to reduce light trespass by requiring luminaires within two-and-a-half times their mounting height from the property line not to produce light across that property line. Many of the light trespass and skyglow criteria are very similar to early light pollution standards put forth by the International Dark Sky Association, and when strictly conformed to, preclude some common lighting approaches. For instance, it is not uncommon to use a decorative style 175W metal halide fixture with cutoff optics. While cutoff optics significantly limit the output above the 90-degree plane, this fixture would not meet the criteria of this credit. Furthermore, the current wording of the credit has produced some confusion since there appears to be conflicts between IESNA RP-33 requirements and light trespass requirements. For instance, RP-33-99 describes lighting criteria relative to four different environmental zones ranging from wilderness and national parks (E1) to city centers (E4). In the environmental zone E4, RP-33-99 limits the amount of light trespass across property lines to 0.6 footcandles, which seems in conflict with Credit 8. As such, in the draft version of LEED-NC 2.2, lighting pollution requirements are explicitly defined in relation to these four zones.

For LEED-NC 2.1 in the Energy & Atmosphere category, Credit 1, 'Optimize Energy Performance,' provides between 1 to 10 credits for achieving various reductions in the energy performance of a building, as compared to the base case of a building compliant with ASHRAE/IESNA 90.1-1999. It is important to note that this credit relates to total building energy performance. Certainly, lighting plays a major role in a building's energy performance, but in order to achieve the reductions required to meet LEED criteria, the design of HVAC systems, which contribute an equally significant if not greater percentage of a building's energy use, must also be seriously considered. There has been little change in this approach in the LEED-NC 2.2 draft version, other than updating the base building standards that reductions are measured against. LEED-CI however, provides up to three credits for reductions in lighting power density below ASHRAE/IESNA 90.1-200, and also provides direct credit for daylight-responsive controls. Given that the draft version of LEED-NC 2.2 was released in December 2004 and LEED-CI was released in November 2004, a mixed message is sent: Will future LEED rating systems only look at whole-building energy performance as in LEED-NC 2.2, or allow direct credits for lighting reductions, as in LEED-CI?

In the current Indoor Environmental Quality category of LEED-NC 2.1, there are no direct credits for lighting systems. Under Credit 6, 'Controllability of Perimeter and Non-Perimeter Spaces,' credits are given for providing occupant controls, but the requirements consider lighting and HVAC together. The Credit 8, 'Daylight and Views,' requirements recognize the benefits of daylighting, but do not provide credit for its integration with electric lighting. In newer LEED products (LEED-CI and the draft version of LEED-NC 2.2), direct credits are given for individual occupant lighting controls. Conspicuously missing are credits available for lighting quality. There has been much talk about providing credits for lighting designed to address the Chapter 10 matrix of design considerations in the IESNA Lighting Handbook, but this has not materialized to date. Regardless, this is not lost on the technical advisory groups developing this category, who will likely recognize lighting quality in some way.

In the LEED-NC and CI/CS products, lighting plays only a marginal role in obtaining any credits in the Materials & Resources category. Under Credit 3, 'Resource Reuse,' and Credit 5, 'Regional Materials,' lighting products can be used in the calculations, but have minor impact. For instance, Credit 5 provides credit if a certain percentage of construction value is achieved using locally manufactured products. With lighting equipment making up roughly only 5 percent of the construction costs, it will not play a large role. Furthermore, under Credit 4, 'Recycled Content,' electrical and mechanical systems are explicitly excluded from the calculations. LEED-EB, on the other hand, has developed a prerequisite for Reduced Mercury Content of Light Bulbs. The metric, picograms of Hg/Lumen-hr, is a newly derived unit meant to recognize long-life lamps while encouraging reduced mercury content. This prerequisite has been contentious due to the calculation requirements and the concern over discouraging the use of energy-efficient fluorescent lamps. The larger issue here is that the lamp is only one component of the luminaire, and while reduction of toxic materials should be encouraged, should mercury be used as a proxy for the full environmental impact of a luminaire? The Materials and Resource category is a sleeping giant when it comes to the subject of sustainability. Understanding how the production of building products affects the environment is a relatively new consideration in mainstream design, and performance metrics are still developing. Hence, there is little information on many systems, including lighting, and credits have been developed based only on information that is readily available, and are therefore not necessarily accurate.

The environmental impact of a product is best understood through a process called life-cycle assessment (LCA), which provides a method for evaluating the environmental burdens associated with the life cycle of materials and services from 'cradle-to-grave,' or preferably 'cradle-to-cradle' (see diagram, page 57). LCA produces quantitative data on 12 impact categories (global warming, acidification, criteria air pollutants, eutrophication, water intake, fossil fuel depletion, ozone depletion, indoor air quality, smog, human health, ecological toxicity, and habitat alteration) resulting from raw extraction, production, use, and recycle and/or disposal of a product or system. Efforts are being made to incorporate LCA metrics into LEED, but it will be a while before such information is available.

It is not uncommon today to see Requests for Proposals requiring firms to address LEED criteria. State agencies are requesting permit applications answer questions related to sustainability, questions derived from LEED criteria. Some cities are even requiring that new buildings be LEED Gold certified. Marginalized in the beginning, lighting is playing a larger role in newer versions, a trend that will continue.

Nicola Ferzacca is the Electrical Department Manager at Symmes Maini & McKee Associates in Cambridge, Massachusetts. He holds a M.S. in Lighting from RPI. Currently, he is serving as chairman of the IESNA Sustainable Lighting Committee, and vice president for the New England IESNA Chapter.