Washington is awash in legislation to mitigate climate change, including proposals for higher taxes on gasoline, caps on carbon emissions and stricter automotive fuel economy standards. Among the most peculiar proposals has been offered by Michigan’s own Rep. John Dingell, D-Dearborn, who is intent on eliminating the mortgage interest deduction for houses that exceed 3,000 square feet in size. The Detroit Free Press, among others, praised Dingell for recognizing that "the only sure way to reduce consumption is to increase costs."

Loss of the mortgage interest deduction certainly would increase homeowners’ costs. But it wouldn’t necessarily reduce energy consumption. In reality, smaller, older homes are far less energy efficient than the
"McMansions" targeted for punishment. According to federal government data, a house measuring about 3,400 square feet consumes about 40.2 Btu per square foot. In contrast, a house of 1,200 square feet consumes 55.9 Btu per square foot—a difference of nearly 16 Btu, or 28 percent.

What Mr. Dingell and the Free Press fail to grasp is that larger homes tend to be newer and thus more structurally sound, better insulated and equipped with more energy efficient appliances. According to the U.S. Census Bureau, only 0.05 percent of houses measuring 3,000 to 4,000 square feet have "serious" structural problems, which is about one-tenth the number of smaller homes with such problems.

Residential energy consumption actually has declined during the past 15 years. Between 1993 and 2001, the number of U.S. households increased by 11 percent but annual energy consumption decreased by 1.4 percent — from 10 quadrillion Btu to 9.86 quadrillion Btu. More energy efficient building materials and appliances have made households far more energy efficient.

Ironically, eliminating the mortgage interest deduction could make housing upgrades too costly for many families — and thus increase rather than decrease household energy consumption.

The Detroit Free Press editorial is available at