If you want to save money on heat, think of your house as one big happy box of cozy warmth. Then find the places where cold air comes in (Hint: Most of it enters through the basement) and the places where warm air leaks out (the attic, primarily, because heat rises).

Then plug the leaks as shown.

Experts call this a whole-house approach, and it's state-of-the-art in thinking about energy efficiency.

Web sites with details for do-it-yourselfers include www.energystar.gov, www.eere.energy.gov/consumer and www.ecasavesenergy.org (click on "Energy Education.")

On Friday, Pennsylvania will launch a new site with energy-saving info at www.energywisepa.org

Seal leaky windows and doors. Use caulk and rope caulk to seal out cold air around windows. Replace broken glass, and reglaze any panes that need it.

Caulk, V-seal, door sweeps and other weatherstripping can provide a tight seal for doors.

Plug holes and add insulation in your attic. Make sure to seal cracks and gaps before you insulate because even small holes in the roof can mean big heat loss. For insulating, consider hiring a pro to get the details right on tricky matters like ventilation and fire safety.

Install an Energy-Star-rated programmable thermostat. Along with plugging leaks, it's one of the best moves you can make in the off-season to save on heating bills. They cost about $50 and can save you maybe $200 a year on heating and air-conditioning costs.

Seal cracks and holes in your basement using caulk for small ones (up to 1/4-inch thick) and expanding spray foam for bigger ones. Pay special attention to gaps along the boundary where your foundation meets your house and to the entry points for pipes and utility lines.

Consider a new furnace. If yours doesn't heat the house comfortably, plugging leaks might be all it takes solve the problem. But if your furnace is more than 10 or 15 years old, it's worth calculating how quickly a more efficient model would pay for itself in fuel savings. Visit go.philly.com/furnace to link to a calculator.