A cover should be placed over the opening of the fireplace at the end of the evening when the fire is nearly extinguished, but hot enough to require an open damper to release smoke. Make certain the cover is tight-fitting around the edges so that room heat does not escape. New technology can improve the efficiency of an existing open fireplace. Open fireplaces exhaust large quantities of air up the flue, resulting in drafts that pull heat out of the home. Thus, an open fireplace only has an energy efficiency of about 5 to 6 percent.
Inserts fill the existing fireplace opening and connect to the existing flue.
These inserts, which use a catalytic combustion system, ensure clean burning and provide a 78 percent efficiency. A fan provides natural convection heating and a thermostat ensures steady, even heat. The type of wood burned also can affect fireplace efficiency. Harder woods, such as birch, oak and maple, burn more slowly and give more evenly distributed heat. Softer woods, such as pine, burn faster and more unevenly.