Fireplaces are cozy and romantic, although not energy efficient: only 10% to 15% of the heat generated actually enters the room and the rest goes up the chimney. But warming your feet in front of a roaring fire on a winter night and the satisfying sound of crackling wood make a home fireplace worthwhile anyway, despite the inefficiency, for many families.

    It’s when the fireplace is not being used and the damper is left open when energy wasted up the chimney is unacceptable. A damper is a simple louver panel or flap in the throat of the chimney above the firebox that opens to let the combustion gases from fire rise up the chimney. It is usually controlled by a lever or pull-chain at the top of the firebox, and should be securely closed when the fireplace is not in use. You may have to lay on your back and look up to locate the damper control for the first time.

    If the damper is left open after the fire is out, you have what amounts to a hole in the roof leaking heated or cooled air into the atmosphere, comparable in size to leaving a small window open. So we recommend checking once in while to verify your damper is securely closed. Also, a damper that is warped by extreme heat or damaged will leak even if closed, and some dampers have a closer that will slip back open slightly after closing that needs adjustment. Another problem is creosote buildup on the damper surface that will keep it from closing completely.

    If a little nudge to remind you to close the damper would help, a small brass “Damper Open / Damper Closed” hanging sign that is about the size of a business card is available at amazon.com for $6.95 + shipping.

   Some older homes from the 1930s and earlier have no damper at all. We occasionally meet vintage homeowners that have never lit their fireplace and had no idea that their chimney was open. Depending on the size of the chimney, a savings of $20 or more per month in energy is there for the taking if you close your damper securely. It’s definitely worth it to keep a close eye on your fireplace damper.

    Also, see our blog post Why is creosote buildup in a chimney dangerous?

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    Here’s links to a collection of our other blog posts about FIREPLACES AND CHIMNEYS:

• What is the 3-2-10 rule for masonry chimneys? 

• Why is creosote buildup in a chimney dangerous? 

• Why does the house have a chimney but no fireplace?

• Why is the chimney leaning away from the house? 

• How is a factory-built fireplace different from a regular fireplace?

• The fireplace doesn't have a chimney. Is that alright? 

    Visit our FIREPLACES AND CHIMNEYS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.