Energy Efficient Fireplaces

There's nothing quite like the warmth and ambiance of a fireplace in the winter. Although they are attractive and can provide heat to their immediate vicinity, fireplaces can actually create a net energy loss. Traditional fireplaces are very inefficient because they draw heated air up the chimney, pull cold outside air into the home, and cause your main heating system to work harder and longer.

Up The Chimney

In a traditional fireplace, roughly 80% of the air heated by the fire is lost up the chimney because the fireplace is pulling the heated air back in to support combustion. Air heated by your main heating system is also pulled up the chimney, often resulting in a net loss of heat. To compensate for the air being drawn up the chimney, outside air is drawn into the house through gaps under doors and around windows, or through other openings. This increases the demands on (and cost of operating) your heating system since it must operate longer to condition the cold, outside air.

Energy Efficient Improvements

There are several ways to improve the energy efficiency of your fireplace, and your comfort as well.

  • The most important thing you can do to improve the efficiency (and safety) of your fireplace is to have your chimney inspected and cleaned. Soot and creosote can build up and block your chimney, putting your home at risk for fire, and they can also prevent the fireplace from getting the necessary oxygen to burn properly.
  • Fireplace dampers should be tightly closed when the fireplace is not in use. The damper should be checked periodically to assure proper closure. If the fireplace is never used, the damper can be sealed with weather-stripping and the chimney stuffed with fiberglass insulation. Of course, this material must be removed from the chimney before a fire is lit in the fireplace.
  • Glass doors act as a barrier against warm room air being pulled up the chimney. Small vents along the bottom or sides allow a controlled amount of combustion airflow into the fireplace. The glass allows the heat from the fire to radiate into the room. Because glass doors reduce the amount of conditioned air that is drawn up the chimney, they also reduce infiltration of outside air into the home.
  • Outside combustion air vents can greatly improve fireplace efficiency. The air needed to keep the fire lit is brought in from outside, not from inside the heated room. This greatly reduces the amount of conditioned air being drawn up the chimney and the resulting infiltration of outside air. The best alternative for an efficient fireplace is to use an outside combustion air vent in conjunction with glass doors. All the heat being radiated from the fire stays inside the room, and none is drawn back into the fireplace and up the chimney.
  • Fireplace inserts or wood stoves are available to fit into an existing fireplace. These inserts are equipped with glass or metal doors, outside combustion air vents, and heat circulation blowers. Fireplace inserts dramatically improve fireplace efficiency by blowing heat from the fire into the room and by limiting the amount of heat and conditioned air lost up the chimney. Fireplace inserts are recommended for fireplaces that are regularly used for space heating. Before installing a fireplace insert, be sure to check the manufacturer's safety specifications and make sure the fireplace insert is compatible with the existing chimney or vent flue.
  • Gas fireplace inserts can be inserted into the cavity of an existing fireplace. They covert the fireplace from wood burning to gas, either propane or natural. If you choose to go with a gas fireplace insert, the chimney must be completely relined and an approved vent installed. For maximum efficiency, look for a unit with an automatic starter instead of a pilot light, and one with variable settings that allow you to turn down the temperature and reduce energy consumption.