A recent study by DOE's Lawrence Berkeley National Lab found that using cool roofs and pavements in cities around the world can reduce air conditioning demand, decrease temperatures for entire cities, and potentially cancel the heating effect of up to two years of worldwide CO2 emissions. The Department also anticipates awarding new projects to develop higher performing, new innovative roofing materials under the DOE's Small Business Innovation Research grant program. See the DOE press release, Secretary Chu's memorandum (PDF 395 KB), Guidelines for Selecting Cool Roofs (PDF 909 KB), Secretary Chu's YouTube video on cool roofs, and the LBNL study.
Home Size is Declining, Energy Efficiency a Factor
The size of new U.S. single-family homes completed in 2009 declined, dropping to a nationwide average of 2,438 square feet and reversing the trend of the past three decades, according to a National Association of Home Builders (NAHB).
New single-family homes were almost 100 square feet smaller in 2009 than in 2007, according to recently released U.S. Census Bureau data. One reason for the drop, NAHB noted, was homeowners' desire to keep energy costs in check.
Despite the tendency toward a somewhat smaller footprint, overall energy use has been growing. One reason could be the spread of air conditioning. Census Bureau data show that less than half of all new single-family homes completed in 1973 had air conditioning while nearly nine-out-of-ten new homes are air conditioned.
Not surprisingly, there are regional differences in those nationwide findings. The proportion of homes with air conditioning ranged from a low of 69% in the West to a high of 99% in the South. The Northeast and Midwest were at 75% and 90%, respectively.
Still, even as energy use climbs, so does energy efficiency. "Residential Energy Consumption Survey," a U.S. Energy Information Administration (EIA) report released in 2005, confirms that while both floor size and overall energy consumption have been trending upwards for decades, energy consumption per square foot has been dropping.
The survey shows that new households were smallest from 1970-1979, averaging 1,863 square feet. They steadily increased through 2005, according to the EIA report. Likewise, overall household energy consumption was lowest from 1980-1989, but has been rising ever since.
However, even as residences have grown, the amount of energy used per square foot has declined from a high of 89 cents per square foot during the 1970-79 decade to 68 cents per square foot in structures built from 2000-2005. See the NAHB press release and page three of the EIA 2005 "Residential Energy Consumption Survey" (PDF 51 KB).
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EREE Network News is a weekly publication of the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE).
