Subhrajit Guhathakurta & Wenwen Zhang, Georgia Institute of Technology, Atlanta, GA, USA
Eric Williams, Rochester Institute of Technology, Rochester, NY, USA
Presentation Title: The impact of neighborhood urban form on household energy use: A case study of Phoenix, Arizona, USA
Urban form, land-use patterns and structures in the built environment significantly influence a city's energy needs, and consequently, its greenhouse gas (GHG) emissions. Engineering and design of urban form is an important strategy for managing climate change and other environmental impacts of energy as well as being key to the livability of cities. This study clarifies connections between urban form and its use together with the associated energy demands for infrastructure (buildings and paved surfaces) and transportation. The model is tested through case studies of two Phoenix sub-areas, one in downtown Phoenix, which is undergoing redevelopment towards higher density housing and the second, a low-density suburban area at the edge of Phoenix, which has undergone significant growth in the last two decades.
Key Lessons Learned
- Energy efficient buildings do not necessarily lead to higher energy efficiency at the neighborhood scale.
- A complete evaluation of all energy use related to neighborhood characteristics suggest that road infrastructure and travel behavior often overwhelm the energy gains from more energy efficient buildings that may be constructed.
- Very high-density buildings that are high-rise and use concrete and steel will have higher energy intensity embedded in the materials and in energy used in construction. Hence, while increasing density of buildings does help in reducing energy used, the overall urban form has a significant impact, specifically in terms of the design of roads and the profile of buildings.
Policy/Practice Implications of Research
These findings have clear implications for urban policies – specifically policies that provide guidance for planning urban neighborhoods:
- Urban development policies should not just focus on one aspect, such as density, but should also contain specific guidelines for ensuring that overall form and transport infrastructure also help in limiting energy use.
- The most pertinent area of regulations that would affect the energy profile of neighborhoods is subdivision regulations; the guidelines on layout of new subdivisions, their plot densities and the network of streets can be significant in reducing urban energy use.
- There are already guidelines and incentives in place for reducing building energy, such as through Leadership in Energy Efficient Design (LEED) certification.
- Recognizing the importance of neighborhood design, LEED for neighborhood development (LEED-ND) is now being vetted and pilot tested for implementation.
- The research provides a methodology for measuring neighborhood energy demands and offers a quantitative basis for making policy decisions.
- Policies aimed at increasing residential density and at regulating the building typology should be part of broader energy conservation and GHG emissions reduction policies at the state and federal level.
Knowledge Gaps and Needs
- Few studies have been able to determine the extent to which people’s behavior is based on their attitudes and cultural traits compared to the environmental context. This particular methodological inadequacy is known as the 'self-selection' bias; and although our measures are able to detect changes in behavior based on the environmental context, the population studied might be especially inclined to such behavior based on their attitudes. More sophisticated tests and longitudinal data are needed to address such biases.
- Introducing energy efficiency in one aspect of lifestyle can lead to a 'rebound effect' on a different aspect, which often reduces the benefits of the first intervention, e.g., those who buy energy efficient cars might be more inclined to drive more often (or buy other energy intensive items) since their disposable revenues have now increased; good estimates of the extent of such rebound effect is extremely difficult.
- The complete portfolio of energy use in a neighborhood, which includes embedded energy in materials, operational energy, and energy used in travel must be further evaluated.