When to Dampen a Chimney

Chimney Damper

• Constructed of steel or cast-iron, the damper in your chimney acts as a doorway between the firebox where you build a fire and the flue that leads up the chimney. When the damper is open, air and smoke from your home have free access to draft up the chimney. When it is closed, no air or smoke can get up into the flue. At the same time, nothing can come down the chimney and into the firebox. Choosing when to dampen a chimney depends on when you are using the fireplace.

Close

• Dampen a chimney, during the winter, if you have no intention of building a fire. Leaving the damper open sends warm air up through it and out the chimney flue. This makes your central heating work harder than it needs to and wastes your money. The warm air going up the chimney is replaced by much colder air from outside, so it is more difficult to keep your home and your family comfortable if you don’t dampen the chimney.

Open

• Open the chimney damper when you plan to build a fire. Before starting the fire, open the damper all the way. The increased air circulation makes it easier to start and build up a fire. Once the blaze is established, close the damper as much as possible without preventing smoke from escaping up the chimney. This keeps as much warm air as possible in your home without causing smoke to back up through the fireplace and become a health hazard.

Considerations

• Always check the damper before starting a fire. Forgetting to do so can fill your home with smoke if you build a fire under a dampened chimney. Chimney dampers often get stuck in the closed position. Moisture from rain or chimney leaks can rust a damper into place over the spring and summer, leaving it nearly impossible to move once fall and winter arrive. Spray-painting the damper with black paint designed to withstand high temperatures can reduce the risk of rusting.