Sharing a wall or two is just a good start, though. In the meantime, there are measures you can take to further stiff the gas man without even leaving the house.
For instance, you can save around 1 percent on heating costs for every degree you lower the thermostat (for at least eight hours a day), according to the Philly-based Energy Coordinating Agency (ECA), which has been raking in federal, state and private grants to help weatherize homes and train people in "green-collar" jobs. That means lowering the thermostat from 70 to 65 saves about 50 bucks for every $1,000 of heating bills.
THAT'S to say nothing of sealing off the third floor that's never used, or letting Junior's bedroom - empty because he's off at college overheating his dorm room - get a little chilly while you stay a little cozier.
Cleaning or replacing air filters works wonders, too. Of course, the proactive approach (spending a little up-front) will work even better, so while you're at it, get your ducts in a row.
In homes with warm-air heating, the ducts often leak as much as 20 percent of the air that comes through, the ECA says, meaning more dust and humidity for living spaces. It could cost you some money for a thorough duct cleaning (low three figures), but at 15 to 20 percent in immediate returns on monthly bills, it'll pay for itself by midwinter.
By adding certain devices to your heating system, from the simple (a flue or damper) to the high-tech (modulating aquastats, which adjust the temperature of hot-water heating depending on the outside temperature), hundreds of dollars can be saved each year, even in small homes.
