UC Berkeley

This dissertation empirically evaluates the association between urban form and the energy performance of neighborhoods focusing on their energy demand and on-site green energy supply. Urban form, the spatial pattern and density of urban physical objects, such as: buildings, streets, vegetation and open space, have a considerable long-term influence on macro-scale environments. Besides their well-known impacts on vehicle trips, the effects of urban form on space-conditioning energy use and on-site energy generation has recently received attention most likely as a result of the energy crisis of the late 2000s.

However, these complex effects of urban form on their net energy savings, generation and potential trade-offs have not been rigorously and comprehensively evaluated due to computational limitations and the lack of data rich environments. In addition, we do not understand what kind of urban form is best for utilizing the benefits from new technologies (for example, efficient vehicles and solar photovoltaics) as they are rapidly being adopted in urban landscapes. Given the inertia of the built environment, it is imperative to alter urban form based on a thorough understanding and comprehensive assessment of urban systems. As our scholarship and practice of green initiatives has been somewhat piecemeal and short-sighted, it is critical that we construct comprehensive models to study the relationships between urban form and energy efficiency.

Given this challenge, this dissertation assesses the impact of urban form on energy use and on-site green energy generation by developing and applying an empirically based data rich model. This research also provides an approach for evaluating potential trade-offs between energy demand and supply given specific urban form. Given these goals, this dissertation focuses on answering three questions that each represent energy demand, supply and trade-offs that are affected by urban form:(1) does urban form have impact on residential space-conditioning energy use?; (2) does urban form have influence on on-site solar energy potential?; and (3) how does the trade-off between vehicle energy use and on-site solar energy potential vary over urban density?

To best account for a complex real-world environment in the model, this dissertation employs advanced three-dimensional urban models derived from Geographic Information Systems (GIS)and Light Detection and Ranging (LiDAR) data. This method successfully captures the physical conditions of real landscapes, including vegetation, which has been impossible to obtain until recent years. After extracting urban form and demographic variables through spatial analyses, it applies multivariate analysis to assess the impact of urban form on energy use and on-site energy generation controlling for other factors. The Cities of Sacramento and San Francisco, California are used in this research, however it is argued the approach is universal in nature.

This dissertation reveals that urban form matters in reducing cooling energy demand and increasing on-site solar energy supply in cities. The results show higher population density, east-west street orientation, higher green space density within a 100ft radius and a higher sum of tree heights on the east, south and west sides of houses have statistically significant effects on reducing summer cooling energy use after controlling for other variables. With regard to impacts of trees on on-site solar energy generation, this research also discovers higher tree density, higher average tree heights and a higher variance of tree heights have significant impacts on reduction in the average rooftop insolation. Examining the trade-off between on-site solar energy potential and vehicle energy use, the results show that the density threshold that allows personal vehicle energy use becomes smaller than rooftop solar potential, changes as vehicle and solar technologies improve and different combinations of them become available.

This dissertation is the first comprehensive validation of many of the early theoretical works on climate responsive urban design and on-site solar energy guidelines in the 1960s through the early 1980s. It supports the argument that more energy related incentives and regulations are imperative not only on a single building scale but also for its neighboring environment on a community wide scale. Finally, this research provides a new approach to how city planners can respond to technological advances and policy shifts in energy related areas.