With winter upon us, the thought of a warm, crackling fire in the fireplace is probably a quite appealing image to a lot of you. What you probably don't realize is that your fire will cost you a lot more than the price of a couple of logs.
Your fireplace is one of the most inefficient heat sources you can possibly use. Basically, you're sending money straight up the smoke stack. While the perception is that you are only sending up heat generated by the fire, the fire must consume oxygen to produce the heat.
Your nice roaring fire can consume and exhaust more than 20,000 cubic feet of air per hour. All that air being exhausted is replaced by cold air coming into the house. The cold air forces your heating system to work hard to warm it up, which is then sucked up by the fire and exhausted through your chimney again. It's an never ending cycle while the fire is roaring meaning that your heater will be working extra hard and costing you money the whole time.
The most energy efficient decision you can make is to not have fires in your fireplace. If you decide to take this approach, consider plugging and sealing your fireplace flue.
While that is the most efficient approach, it isn't a whole lot of fun. A winter fire is nice to have once in awhile. If you know there will be occasions when you will want to have a fire, there are still some things you can do to make the fire as energy efficient as possible. You'll want to keep your fireplace damper closed at all times except when a fire is going. Accidentally leaving the chimney flue open is like leaving a two foot square window open. You also want to make sure that when the damper is closed, it closes snugly and doesn't leave gaps where air can escape.
Most fireplace dampers are form fitting which prevents air leakage when they are closed. As years pass, however, the damper metal can warp due to the heat from the fires and moisture from the outside. This can cause the seal to loosen which will allow room air to escape up the chimney. Close the damper and light a candle to see if it flickers when placed near the damper seal. If it does, you need to either repair or replace the damper to close the leak.
When you do have a fire going, open the dampers at the bottom of the firebox if your fireplace has them. If not, open the nearest window to the fireplace about an inch and close all the doors to the room. This allows the fire to consume fresh air that hasn't been heated before exiting up the chimney again. You should also lower your thermostat setting to approximately 50°F while the fire is going to make sure your heating system isn't heating air that will soon be leaving up the chimney.
Making sure that your damper is always tightly closed when not using the fireplace and following the above steps when the fireplace is in use can save you hundreds of dollars in energy costs each winter that you probably didn't even know that you were wasting.