Currently, the leading method of green building certification is the Leadership in Energy and Environmental Design (LEED) rating system. The LEED system was developed by the U.S. Green Building Council (USGBC) in 1998 as “a consensus-based, market-driven building rating system designed to accelerate the adoption of green building practices” by creating widely accepted and regimented performance criteria. The main aim of the LEED certification process is to promote design and construction habits that increase profitability; improve occupant health and well-being; and reduce the negative environmental impacts of building site selection, energy and material usage, and environmental air quality. A total of eight LEED Rating Systems exist, covering almost all building and construction types.
The most commonly implemented system is LEED for New Construction (LEED NC), which serves as the basis for this analysis. LEED NC “addresses design and construction activities” for both new commercial, institutional and residential buildings, as well as major renovations of these existing buildings (GBCI 2010). The LEED NC program awards credits on a 100-point scale and ensures that buildings are strategically designed to improve performance across the following categories:
• Sustainable sites (SS)
• Water efficiency (WE)
• Energy and atmosphere (EA)
• Materials and resources (MR)
• Indoor environmental quality (EQ)
Eight prerequisites must be satisfied to qualify for a LEED certification, and a possible ten bonus points can be achieved through innovation in design and regional priority credits. An individual credit can earn multiple points, and not every credit is applicable to each project.
LEED projects can earn a Certified, Silver, Gold, or Platinum distinction depending on the number of sustainable attributes implemented. Although the structure for earning points is relatively simple to comprehend, achieving a desired number of points requires creativity, integration, and analysis. This is especially true of the Gold and Platinum distinctions, which require significant effort and ingenuity from project designers to push the boundaries of sustainable building design and lead market transformation Proponents of the LEED framework note that the system is straightforward, delivers a market-respected metric, and appeals to human nature. These qualities have led to the widespread adoption of LEED as the industry standard. To further simplify sustainable construction, the USGBC offers extensive LEED training programs, an Accredited Professional exam, templates, and technical support. The system permits flexibility in the design options used to achieve each credit, employs regional credits to adapt to site-specific needs, and values the fact that various building types require particular rating systems. The underlying theory behind the LEED system is that architects, engineers, and developers are expected to adopt a more adaptive approach to building design.
While the LEED system encourages holistic design and represents an evolution of systems thinking concepts, detractors note that the philosophy does not always translate to practice. At present, the LEED rating system is undergoing its third revision. This indicates both adaptability towards trends in technology use and potential system flaws. For example, credit weighting is new to the latest revision and is an attempt to rebalance credits and ensure Energy & Atmosphere (EA) credits are pursued. Evidence that highly sustainable measures, many of which are encapsulated in the EA credits, are not often pursued uncovers an unfortunate mismatch. Behavioral and implementation issues surrounding the efforts of designers and developers tend to relegate the LEED certification process to a point-grabbing game, rather than the way to encourage sustainable building design that its developers had intended.
This analysis attempts to address the three following questions: How does a developer determine what LEED standard to achieve? Which credits are worth the capital investment? What is going too far? This analysis takes the perspective of a developer who wants to build a new LEED-rated mid-rise apartment building due to the fact that renters are typically willing to pay a higher price if they are living in a “green building.” The developer faces a two-headed question: how many credits should be obtained, and which specific credits are economically, structurally, legally, and aesthetically feasible? This analysis takes a systems approach that consists of establishing an objective function that is governed by a set of constraint equations. The objective function, below, maximizes the number of LEED credits earned for a new multi-family residence.