Air rushing in through the foundation was only part of the problem, however. Much of the rest was air seeping out of a closet on our second floor, where a small furnace unit was located. The closet had never been completely drywalled, so air filtered through insulation in the roof to the great outdoors. Minch recommended we finish the drywalling when the time comes to replace the furnace.

Minch also gave us tips about lighting and appliances. "A typical kitchen these days has ten 75-watt spots on all day," he said. "That's a huge waste of money." Replacing them with compact fluorescents could save a homeowner $200 a year. Refrigerators, washing machines, dishwashers, and other appliances, in fact, may represent half of a household's electric bill. Those with Energy Star labels from the EPA are more efficient and may come with rebates or tax credits when you buy them, Minch said.

There was no shortage of advice out there, I discovered, about ways to cut back on CO2 emissions. Even before Minch's visit, I'd collected stacks of printouts and brochures from environmental websites and utility companies. In a sense, there's almost too much information.

"You can't fix everything at once," John Bauer said when I asked how he and Kyoko were getting along. "When we became vegetarians, we didn't do it all at once. First the lamb went. Then the pork. Then the beef. Finally the chicken. We've been phasing out seafood for a few years now. It's no different with a carbon diet."

Good advice, I'm sure. But everywhere I looked I saw things gobbling up energy. One night I sat up in bed, squinted into the darkness, and counted ten little lights: cell phone charger, desktop calculator, laptop computer, printer, clock radio, cable TV box, camera battery recharger, carbon monoxide detector, cordless phone base, smoke detector. What were they all doing? A study by the Lawrence Berkeley National Laboratory found that "vampire" power sucked up by electronics in standby mode can add up to 8 percent of a house's electric bill. What else had I missed?

"You can go nuts thinking about everything in your house that uses power," said Jennifer Thorne Amann, author of Consumer Guide to Home Energy Savings, who had agreed to be our group's energy coach. "You have to use common sense and prioritize. Don't agonize too much. Think about what you'll be able to sustain after the experiment is over. If you have trouble reaching your goal in one area, remember there's always something else you can do."