How to Adjust a Fireplace Flue

Even though fireplaces are warm, cozy, inviting and restful, they are one of the biggest energy wasters in our homes. Warm air from the house is pulled up the chimney, while cold air from outside is pulled into the house wherever it can enter, including around leaking windows and doors. This is known as convection. The best way to minimize the amount of warm air leaking up the chimney is to adjust the flue. Ideally, the flue should be open just enough to pull smoke from the fire up the chimney. Begin with the flue open all the way, and adjust the flue after you have built a fire.

Instructions

1. Find the lever or chain to operate damper and flue. Before you light the fire, stick your head into the firebox and look up. You should see either a metal lever or set of two pull chains, usually with rings at the ends. The flue is opened using the lever or chains. If there is a lever, try pushing it up or down. If it moves, look up the chimney. If the damper has opened the flue, you should see the sky. If the lever does not move up or down, try moving it side to side. If your fireplace has a set of chains instead of a lever, one chain opens the flue and the other closes it. Pull on the chains until the damper is activated. Once the damper has opened the flue, you will see the sky when you look up the chimney.

2. Build a fire. In order to get the flue and damper system working most efficiently, you need to make a good-sized roaring fire. During this step, the flue and damper should be open all the way.

3. Adjust damper opening. Once the flue and damper have heated up from the fire, begin closing the damper a little at a time. Keep adjusting until the airflow from the house through the fireplace and up the chimney is at a minimum. After the flue and damper heat up from the fire, they are easier to move--but also hotter. Protect your hands when operating the damper and flue lever. The damper should be open just enough for the flue to transport smoke from the fire up the chimney.

4. Close the glass fireplace doors. This will prevent warm air in the house from being sucked up the flue.

Tips & Warnings

• The chain or knob to open and close the damper and flue will become hot from the heat of the fire. Use protection for your hands when adjusting these once you have built a fire.