Use Performance-Based Transportation Credits in LEED
Back in August 1999, I participated in a U.S. Green Building Council (USGBC) charrette to craft the LEED 2.0 Rating System from the original LEED 1.0 pilot. The small workgroup focused on site and ecosystem issues, in which I participated, sought to remove any bias that encouraged building on previously undeveloped sites. We ended up with five credits that provide points for development density, access to public transit, bicycle storage and changing rooms, infrastructure for low-emitting vehicles, and limitations in parking capacity. While some have poked fun at credits for bicycle racks and vehicle charging stations, these five credits have brought the important issues of location and transportation to design teams.
Our research on “transportation energy intensity” (see Driving to Green Buildings: The Transportation Energy Intensity of Buildings) has helped me appreciate just how important site selection and transportation are. We found that an average commercial office building in the U.S. built to ASHRAE 90.1-2004 energy standards is responsible for more than twice as much energy in getting workers to and from work as the building itself uses in its operation. If the average commute distance is greater than the national average (12 miles one-way) the transportation fraction of a building’s energy use may be even greater. As covered in the accompanying feature article, a wide range of strategies—most having to do with land-use planning—can significantly reduce this transportation energy intensity of a building.
While the prescriptive approach in LEED to site and transportation issues has served an important role, it’s time to provide a more rigorous basis for these credits. Specifically, I believe that the points addressing transportation should be changed from a prescriptive basis (provide bicycle racks, limit parking, etc.) to a performance basis. To do this, USGBC should champion research to develop building-specific metrics for measuring the transportation energy intensity of new and existing buildings. A huge body of research has already addressed these issues, but that research has been done largely on a community scale. To be used in LEED for New Construction and other building-specific LEED rating systems, we need building-specific metrics. (This research need is included in the National Green Building Research Agenda being developed by the USGBC Research Committee, on which I sit [see EBN Vol. 16, No. 6].)
USGBC should articulate the specific needs for such performance-based metrics and assemble a team of the leading experts in transportation and land-use planning to develop those metrics. The end product might be a “transportation energy intensity” spreadsheet that would be used for a building going through LEED certification. A dozen or so factors would be entered for such attributes as distance to public transit, neighborhood density, limitations on parking, access to bicycle and pedestrian pathways, and streetscape design amenities like traffic calming that encourage pedestrian use.
By filling in the submission form, the user would end up with a weighted adjustment factor that could be used to calculate performance-based LEED points. As actual performance measurements are taken of the transportation energy intensity of completed LEED buildings, USGBC could improve these formulas, making LEED more scientifically rigorous and improving the environmental performance of future LEED buildings.