that they would be unrealistic absent a strong state or regional role in growth management.


Improved Energy Efficiency of Residential Buildings

The prior sections have focused on the potential savings in energy use and CO2 emissions from reduced travel associated with more compact, mixed-use development. Another important source of savings, directly related to more compact development, is the improved energy efficiency of residential buildings. The U.S. residential sector accounts for slightly more than one-fifth of the nation’s total annual energy use and produces an equivalent share of total annual CO2 emissions (EIA 2007).22

Substantial savings in energy use and CO2 emissions can be achieved through improved building design, primarily by increasing the thickness of insulation and by realizing changes in home size that would result from more compact development (Kockelman et al. 2009). For example, moving from a single-family to a multifamily DU would result in significant energy savings. Calculations conducted for this study revealed that moving from a 2,400-ft2 single-family home—the average home size in the United States in 200723—to a 2,000-ft2 apartment would save about 34.1 million Btu and about 3.3 metric tons of CO2 emissions, all else being equal (see Annex 5-1 Table 5 for detailed calculations).24 By


Of the four end-use sectors—transportation, industrial, commercial, and residential— the residential sector accounted for 20.7 percent of consumer expenditures for energy and 20.4 percent of CO2 emissions (EIA 2007, Tables 3.6 and 12.3).


According to the National Association of Homebuilders (NAHB 2007), the average new one-family home is slightly larger inside metropolitan statistical areas—about 2,500 ft2. Average home size has been rising at a rate of approximately 30 ft2 per year over the past decade.


As part of a larger paper on options for controlling greenhouse gas emissions (Kockelman et al. 2009), Charlotte Whitehead of the University of Texas at Austin, one of three student researchers, performed these computations. Using the Residential Energy Consumption Survey of the Energy Information Administration, she selected 20 sample cities, reflecting different climate zones and census regions, to develop regressions of home and apartment energy use as a function of various DU and household attributes.

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