Sunday, December 19, 2010

LEED ND - Great System, Room for Improvement

Many have waited years for the release of the USGBC’s LEED ND rating system. The LEED ND system “was designed as a market transformation tool” and is the most holistic LEED system released to date by requiring “the neighborhood… to be situated in a place that makes sense from a transportation standpoint.” Some have even claimed that this is the USGBC’s attempt to “set (the) first national standard for neighborhood design.”

There are many positives for the rating system and building sustainable neighborhoods. Village Homes in Davis, California is often used as a case study for “bottom line savings associated with green communities” (Baker 2007). The community was built in the 1970s and homes now “command $10 to $25 more per square foot than those of surrounding subdivisions.”

However, there is room for improvement. USGBC fees impact certain projects, potentially causing some projects to forgo results for documentation. Another criticisms stems from how credits are weighted in the system. Looking specifically at the LEED ND system, few technical issues arise. Lastly, long-term metrics should be incorporated into the system also focusing on the issues of causation and mode choice.

First, let’s examine the USGBC fee structure. For instance, if the goal is to provide sustainable low-income housing, how do the USGBC fees play into the financing? Are projects paying for documentation and not results? Do the fees stifle smaller projects with more restrictive budgets? And, if the goal were to produce the most sustainable projects, would it not seem more critical to invest the money to further the project than to receive a credential?

Another large criticism against the LEED rating systems is how credits are weighted. For example, the LEED ND environmental categories are approximately evenly weighted. But the Smart Location and Linkages category is by far the most important in shaping change from a land use perspective. Even factoring in the few points available for Regional Priority does not weigh heavily enough on overall environmental priority. The Bicycle Network credit and the Minimize Site Disturbance During Construction credit both receive one point, even though the network might be easier to implement, it may be far more important than other credits with higher ratings.

The rating system has been through many revision processes and vetted through USGBC, CNU, and NRDC. During the revision process many changes were made to the SLLc3 for locations with reduced automobile dependence by increasing levels of transit service. Overall, the threshold was raised and the credit requires that the transit must be in place, not planned for the future. Other revisions updated the Walkable Streets Prerequisite to limit garages in the front of homes, “only 20% of street frontages may be occupied by garages.”

Additionally, the SLL prerequisite for location is “the most important single standard.” Under option 3, the prerequisite requires development to locate “on a site with existing and/or planned transit service such that at least 50% of (the) dwelling units and nonresidential building entrances are within a ¼ mile walk distance of bus and/or streetcar stops, or within ½ mile walk distance of bus rapid transit stops, light or heavy rail stations, and/or ferry terminals.” With the latest revisions, development may achieve this prerequisite by locating near “planned transit as if they have actual, existing transit service” even for bus routes which are less certain. The prerequisite should be stronger, requiring development around existing transportation nodes. There is similar criticism for the NPDC3 Mixed Use credit allowing planned land uses to count towards compliance, where uses should already exist.

The recent revisions also weakened other credits such as the Wetlands and Water Body prerequisite. The required buffer dropped from 100 feet to only 50 feet. There are many credits aiming to protect or restore wetlands. Understandably, their aim is to protect these fragile areas, what happens if a project does not even have areas defined as wetlands? There are four credits with four points that are not applicable for these projects. Is LEED ND encouraging development near wetlands, in order for developers to avoid disturbance and obtain a credit? Would it not be best to just develop on lands not containing wetlands?

The potency of other credits was also diminished. The Agricultural Land prerequisite was minimized with the new standard requiring “mitigation, but only for the lowest-density projects" and exempting projects served by transit or planned transit. In NPDC9 Civic and Open Spaces, parks do not receive any specific credit. Certain credits should be required, like historic preservation and rightfully so, it is often argued that older buildings are more energy efficient and their character adds to the charm of the neighborhood.

Overall, credit achievement should be based on existing conditions to strengthen infill development and accurately reflect the sustainable design goals inherent in LEED ND rating system. The rating system has many achievements, but the credits are “disproportionate to their effect on environmental performance” where location should outweigh design. Lastly, allowing projects to achieve an extra point for having a LEED Accredited professional seems like an act of self-promotion. Smaller projects may not be able to afford such expertise and should not be disadvantaged for such reasons.

The LEED ND rating system is also lacking long-term metrics to measure future usage. Will projects maintain their low income housing balance? Will transit infrastructure and bicycle lanes be maintained? The LEED ND credential should not be a box that is simply checked at the end of the project, when the project’s life begins at occupancy. Follow up measurements should be developed to ensure that projects continue to operate with LEED ND’s design intent.

Lastly, the rating system provides many opportunities to create vibrant spaces to entice pedestrians and use of alternative transportation. However, the system does not factor in the element of choice. If LEED ND projects are encouraged to infill or located near existing neighborhoods, what is the existing mode share for that area? Do people that enjoy walking, choose to live in certain neighborhoods? How does this effect the design considerations set by LEED ND? Would these projects attract people that already have a predisposition to alternative transportation?

Similarly, are people moving to LEED ND communities that already use alternative transportation? Are we simply moving people to newer walkable communities, or are LEED ND projects helping reduce vehicle miles traveled? How do the vehicle miles traveled in a LEED ND community compare to the neighboring communities?

Implementing a LEED ND project helps continue the walkable street pattern. People “walk more if they move to a neighborhood with a more attractive appearance;” however, “changes in the built environment are important, but apparently no more so than other variables, including attitudes and preferences.” LEED ND should attempt to measure attitudinal elements as factors of project success.