In an ongoing series, I’ve been trying to define areas of the Twin Cities metro that are “location efficient” using the USGBC’s LEED ND rating system. The previous posts focused on those requirements of LEED ND that cannot be met through the design of the project itself: features of the built and natural environment that determine a minimum eligibility for LEED ND based on location. This resulted in a map of areas in the region that met this basic level of “location efficiency”.
However, there are a few other requirements of LEED ND that can technically be met through the project design, but may not be able to be met in reality based on the existing built environment, or the current planning or zoning rules in a particular location. For example, LEED ND requires a minimum density for both residential and non-residential uses. Technically the density of the project is controllable by the project designer, however, if a city has land use regulations in place that only permit densities lower than what is required by LEED ND, plan and zoning amendments or variances would need to be granted before the project could go forward, all of which are not certain. Many communities are averse to the levels of density required by LEED ND, and therefore elected officials would be unlikely to grant such changes to land use regulations.
The two requirements of LEED ND that fall into this “semi-controllable” category are NPD Prerequisite 2 and NPD Prerequisite 3. As mentioned above, NPD prereq 2 is about minimum density, with requirements for residential and non-residential uses. The very minimum required for residential uses is 7 units per buildable acre of land. The minimum for non-residential is 0.50 Floor Area Ratio (FAR).
NPD prereq 3 requires a certain density of streets within and around the project area. While this is under the control of the project designer if the project has internal streets, it is not if the project doesn’t have internal streets.
Planned Land Use Density
Planned land use from the adopted 2008 comprehensive plans can be used to identify areas that are permitted to achieve at least 7 units per acre and areas planned for commercial, industrial, mixed-use or other non-residential category. Since planned land use doesn’t often identify non-residential density, I had to assume that all of these areas would qualify for NPD prereq 2 since I didn’t want to read 180 plus zoning ordinances.
Mapping the areas where land use regulations allow this density of development shows that this prerequisite reduces the eligible area of the metro quite significantly from what the first analysis of “location efficient” sites showed. There are few areas outside of Minneapolis and Saint Paul that are eligible, primarily because planned housing densities are too low.
Street Intersection Density
NPD prerequisite 3: Connected and Open Community requires that projects meet a certain intersection density. For projects with internal streets, this must be 140 intersections per square mile. For projects without internal streets, the minimum is 90 intersections per square mile. Since this analysis does not take into account project designs, I’ll just assume the minimum must be 90 intersections per square mile.
Measuring intersections can be a little tricky since alleys and non-motorized right of way can count, and there isn’t a good regional layer for all these. Also my method for measuring intersection density is not perfect for every location, so I’ve reduced the threshold slightly to add a little fudge factor. This map shows areas that meet this minimum density of intersections.
Good and Better
Areas identified as eligible in Part 2 were considered “location efficient”, however, that assumption was independent of the regulatory and built environment constraints identified in NPD prereq 2 and 3 discussed above. So areas in Part 2 could be described as having “minimal location efficiency”. Areas eligible in Part 2 AND meeting NPD prerequisites 2 and 3 could be described as having “high location efficiency“. These areas would be far more likely to be eligible for LEED ND because land use regulations are already in place that allow development at appropriate intensities, and the street network is dense enough to support transportation modes besides the automobile.
How Should We Plan?
This series is intended to be an exploration of planning for a sustainable region. That means guiding future growth to locations that would use infrastructure efficiently, promote human health through built form and protect sensitive resources, among other things. How can we use the LEED ND framework presented here to do this? In a future post, I plan to look a little bit at how our existing regional planning framework and processes could be modified, using this information as a guide, to promote more sustainable growth.