If U.S. home energy consumption were a country, it would rank as the world's sixth-largest greenhouse gas emitter. To bring housing emissions in line with international goals to limit global warming, planners must sift through variables such as local climate, building age and size, and occupant income.
A recent study in the Proceedings of the National Academy of Sciences USA provides a new nationwide analysis evaluating these factors. The researchers fed detailed building data from 93 million homes (gleaned from a database of U.S. tax assessor records) into computer models that accounted for local fuel sources to estimate home emissions.
One clear result was that wealthier people's homes in America tended to be larger and produce about 25 percent more emissions than those of low-income people. This relation held when the researchers dug down to compare neighborhoods within very different cities such as Los Angeles and Boston; in L.A., for instance, some affluent neighborhoods had emissions 15 times higher than nearby low-income areas.
Study co-author Benjamin Goldstein, a researcher at the University of Michigan, was surprised by another finding: dense apartment complexes are not essential to meet emissions goals. The data suggest single-family housing on small lots in certain areas, such as some in Los Angeles, could also reach international targets as carbon-free energy sources become more common. “Not everything needs to look like Brooklyn or Manhattan to be low energy,” he says.
Anu Ramaswami, a Princeton University environmental engineer, who was not involved with the study, cautions that its emissions-estimating models may not capture efficiency measures taken by some homeowners. But she says the research could set an example for municipality-level analyses. For example, such studies could help officials determine how to tailor specific local building policies to best reduce emissions, such as by encouraging smaller lot sizes or alternatives to heating oil.