Green neighborhoods can reduce the greenhouse gas emissions related to daily life if their location puts residents close to jobs, businesses, and recreation. Design and density also play an important role.

The Urban Land Institute and Smart Growth America released the Growing Cooler (1) report in fall 2007, summarizing current research about the relationships between urban development patterns and travel-related greenhouse gas emissions.

Four factors are important: location, neighborhood design, density, and mix of uses. 

• Location: Growing Cooler reports that more central locations are as important as all three other major factors combined.  Similarly, another recent study (2) found that residents in neighborhoods in inner areas have 36-60% lower travel-related greenhouse gas emissions than those in outer areas.

• Pedestrian Design: Growing Cooler found that design – described as an aggregate of street network density, sidewalk coverage, and route directness – has a significant impact on greenhouse gas emissions. A recent Canadian study found that residents of mixed-use neighbourhoods with a tight network of streets would have 24 to 50 percent lower travel-related greenhouse gas emissions than those in purely residential neighborhoods with large blocks and cul-de-sacs.

• Density: All else being equal, doubling density will reduce travel-related greenhouse gas emissions by 5%, according to Growing Cooler.  However, reduction in vehicle travel is exponentially related to increasing density of jobs and housing – so achieving densities of at least 15 units per acre (3).

• Mix of uses: mixing uses produces similar reductions to increasing density and interconnected neighborhood design.

A good example of the way green neighborhoods can reduce use of cars is the Atlantic Station project, a 138-acre high-density brownfield redevelopment in Atlanta, Georgia. A modelling study forecast that its development would result in 35 percent less driving and emissions than if development occurred on alternative suburban sites. These results were so striking that the project was deemed a transportation-control measure to help the city meet air quality regulations.

Travel accounts for around half of neighborhood greenhouse gas emissions, depending on where you are. Other factors include:

• Building energy performance: Discussed in the buildings section, minimizing building energy use is an important opportunity for action.

• Neighborhood-scale energy systems can achieve substantial further reductions. District Energy Systems can be much more efficient than heating/cooling systems for individual buildings.  Often provided through partnerships with utilities, this energy infrastructure can be implemented as a retrofit or in new neighborhood developments.

• Green networks help: Nationally, trees store between 660 and 990 million tons of carbon. Trees that shade homes also reduce the need for air conditioning by 20-25%, reducing related energy use and GHG emissions.

References:

(1) Ewing, Reid, et. al.  2007.  Growing Cooler: The Evidence on Urban Development and Climate Change.  Urban Land Institute.
(2) IBI Group, 2002.  GHG Emissions from Urban Travel.  Canada Mortgage and Housing Corporation / National Research Canada.
(3) Newman, Peter and Kenworthy, Jeffrey. 2006. Urban Design to Reduce Automobile