Ten to 20 percent of warmed air from your home can be drawn into the chimney flue, passing around a rusted, stuck, or loose-fitting damper.How to spot it:
With the damper closed, hold a lit candle inside the firebox and watch the flame. If it gets beaten around or blown out, air is flowing up the chimney. How to stop it:
Hire a chimney sweep. In addition to giving the chimney a good cleaning, lubricating and checking the damper is usually part of the $90 to $200 service call. In the off-season, when the fireplace isn't in use, you can seal the flue completely with a balloonlike plug, such as the Fireplace Draftstopper ($55; batticdoor.com
), that you inflate and insert up the chimney just in front of the damper. When cold weather starts again, simply deflate the plug for easy removal. The payoff:
Reduce your annual heating bill by up to $500.