Many new furnaces on the market are 25 percent to 40 percent more efficient than older models. The Environmental Protection Agency's Energy Star program promotes furnaces using "condensing technology" as the most efficient.
This technology takes advantage of normally exhausted heat in furnace flue gas to improve efficiency. Instead of venting the combustion gases directly outside, the gases are captured and used to heat the air even more.
The efficiency rating on the label of every new furnace tells how much of the total energy that the furnace uses will be delivered to the home as heat. The higher the rating, the better.
If you already have a newer furnace, it's best to have it serviced sooner than later, because the dance cards at utilities and fuel-oil companies fill up quickly as chilly days approach.
When cold weather does arrive, monitor your thermostat, setting it as low as you find comfortable. The Energy Department suggests rolling temperatures back 10 to 15 degrees before bed and before leaving for work.
Utility companies simply recommend setting your thermostat at 68 degrees or lower during the day, "health permitting," then setting it lower at night or when you'll be out more than four hours.
Weatherize away. If your furnace is efficient to the max but the heat escapes, what's the point? Leaky windows and doors can be big sources of heat loss, so don't skimp on the weather-stripping around them.
If you have particularly leaky windows, you may want to use plastic covers that shrink onto them. They're less unsightly and damaging than stapling plastic to the window frames.
Plugging air leaks can save you up to 10 percent on energy bills, and is probably the easiest way to cut costs.
To decide where to install weather-stripping, try the candle test: Light a candle and move it around the window or door on a windy day. Note where the candle flickers; that's where the weather-stripping goes.
Make sure your windows have no cracked or broken panes. To extract a broken pane, remove the putty and glazing points, then have a piece of glass cut to fit, replace the points, and reglaze.
Check rubber seals around the glass of storm doors and windows. If they must be replaced, install weather-stripping rated for exterior use. Weather-stripping or caulk costs $2.50 to $5 at home centers and hardware stores.
Basement windows tend to be the worst cared for, so make sure too much air isn't escaping through them.
Seal before you insulate. As warm air flows out of a house, cold air is pulled in to replace it, since the air pressure inside must equal the outdoor pressure. The temptation, of course, is to turn up the thermostat, but heat will still head for the door, and you'll still be cold.
What about insulation? Great idea, but experts say that before you insulate, you need to use foams and sealants to close any penetration to the outside, such as at the ends of joists at the front and back of the house.
Sealing - tucking white or black plastic bags into the cracks (clear ones decompose) - prevents heat from escaping and moisture from entering an attic, without interfering with the required ventilation. Then you can go ahead and insulate.
Air sealing and insulating properly and efficiently is where professionals can come in handy.
But adding insulation to the attic is a good do-it-yourself task. Take the proper precautions, wearing loose-fitting clothes and a mask and safety glasses.
Insulation isn't all that expensive. For maximum energy efficiency, Owens Corning recommends an insulation value of R-60 for attic floors, or about 18 inches of insulation. R-value calculators can be found at several Internet sites.
Mind chimneys and fireplaces. Make sure you inspect the chimney. The mortar in the joints between the bricks should not be loose or missing. When water gets into joints with loose mortar, freezing and thawing can turn it to powder.
Have the fireboxes in wood-burning fireplaces cleaned and the creosote removed.
Troubleshoot all around. Trim tree limbs that hang over the roof. The weight of ice or heavy wind can cause limbs to damage the roof or power and phone lines.
Check your gutters and downspouts. Sometimes they pull away from the edge of the house or get out of alignment. Clean out leaves and other debris and repair any holes that have developed in the trough.
That should keep you busy for awhile.
Contact Alan J. Heavens at 215-854-2472, firstname.lastname@example.org, or follow @alheavens at Twitter.