-By Barbara Horwitz-Bennett

Although the ever-popular USGBC's LEED certification programs offer generally clear-cut, distinctive guidelines for their different rating systems, occasionally designers face a dilemma as to which rating system to pursue for a particular project.

"For the most part, many projects will be able to clearly fit within the defined scope of only one LEED rating system," explains Carlie Bullock-Jones, ASID, LEED AP, sustainable design consultant at EcoWorks Studio in Atlanta. "However, sometimes it's possible that two or more LEED rating systems may be viable options."

For example, Brian M. Malarkey, AIA, LEED AP, executive vice president and director of Kirksey EcoServices in Houston, brings the case of a speculative office building interested in LEED for Core and Shell (CS) certification, while a number of its tenants may want their spaces to be certified by the Commercial Interiors (CI) system.

Or take mixed-use projects: "This is a hot topic, and there is not a clean solution," states Malarkey. "Mixed-use involves retail, which is difficult to control in terms of what kind of materials and systems are installed within the many spaces that are leased to the retail tenants."

What to do?

Laying out some general guidelines, Doug Gatlin, vice president, market development for the Washington, D.C.-based USGBC, explains, "LEED for Existing Buildings: Operations & Maintenance is not for construction or major renovation, rather it is for improvement of the HVAC, electrical, and plumbing systems, and also for implementing best practices in terms of management and policies, such as a green cleaning or recycling program.The scopes for NC versus CI are also clear. NC is for whole building design and construction, while CI is defined by the tenant area."

In terms of a practical approach to the mixed-use question, Ken Wilson, AIA, IIDA, LEED AP principal at Envision Design in Washington, D.C., suggests, "In a mixed-use project, one should pursue the certification that represents the largest part of the project. For example, a new multi-family housing project with a small retail component would pursue LEED-NC, even though the retail part might be best represented by LEED-CS."

And in Russell Perry's experience as an AIA, LEED AP, and the director of sustainable design in SmithGroup's Washington, D.C., office, he relates: "When faced with these ambiguities, we typically take the time to run likely scenarios through both rating systems to see which rating system fits best with the anticipated design."

Similarly, Sandy Mendler, AIA, LEED AP, at Mithun in San Francisco, advises, "For cases on the borderline, I would recommend that both systems be looked at to glean the best design advice because the whole purpose of the rating system is to support good decision making."

In general, Bullock-Jones suggests the following steps to help building teams determine the optimal rating system for a project:

• Review and understand the rating systems currently offered by referencing www.usgbc.org.

• Review the certification process, requirements, and expectations for each system.

• Look at the Web site's Credit Interpretation Rulings, which may address questions posed by similar projects as to what certification to pursue.

• Look at LEED project case studies, which, again, may include cases similar to the project in question.

• If there is still some doubt, contact the USGBC to seek additional guidance.

Deciding early

One point on which most designers agree is the importance of determining up front which LEED rating system to pursue. "It is important to establish goals early and have a strategy in place so that the process can be streamlined," stresses Wilson. "You don't want to waste time and the client's money pursuing credits that might not apply to your final certification type."

In addition, Eric Anderson, AIA, LEED AP, senior associate at MulvannyG2 Architecture in Bellevue, Wash., points out that LEED requirements may change over the life of a project, so committing to credits early in the process is essential. "If you have locked in your design credits early for all the buildings on your campus, you won't be required to make changes that could impact subsequent buildings, change the overall look and feel of your campus, or prevent you from achieving the targeted rating."

At the same time, Anderson adds that there is "wiggle room" during a project's schematic design phase if the building team is still trying to determine which LEED rating system will work best for the project.

On the horizon

Even though designers sometimes may be faced with challenging LEED decisions, as the system continues developing, such dilemmas are expected to become much less frequent.

"LEED is continually evolving, and the USGBC is currently working to make the LEED rating system more flexible and streamlined to address various markets, project scopes and types," says Jones.

Backing up Jones' statement, Gatlin adds, "In 2009, we will launch a Web-based tool that will help with project selection automatically.However, the basic criteria are very similar in most rating systems—mandatory air quality and temperature control requirements, focus on energy efficiency, water efficiency, use of recycled/sustainable materials, waste minimization, and transit-friendly location.Keeping one's sight set on these principles will help provide clarity to the rating systems and ensure the delivery of a solid project."