About 2.9 million households use wood as their primary heating source, and 8.9 million homes use it as a secondary heating source. Newer wood and pellet-burning appliances include models that are cleaner burning, more efficient, and powerful enough to heat many average-sized, modern homes.
Traditional open masonry fireplaces should not be considered heating devices. Traditional fireplaces draw in as much as 300 cubic feet per minute of heated room air for combustion, and then send it straight up the chimney. Fireplaces also produce significant air pollution. When burning a fire in a traditional fireplace, you should turn your heat down or off and open a window near the fireplace. Close the flue when the fireplace is not in use. Consider installing an inflatable flue stopper in rarely used fireplaces or during summer months to stop air leaks.
Pellet stoves, which burn small pellets made from compacted sawdust, wood chips, bark, recycled paper, or agricultural crop waste, are among the cleanest wood-burning options. They have combustion efficiencies of 78%–85%, heating capacities of 8,000 to 90,000 Btu per hour. They can be direct-vented to the outside and do not need a chimney. They require electricity to run the fans, controls, and pellet feeders.
Masonry heaters, also known as “Russian,” “Siberian,” and “Finnish” fireplaces, produce more heat and less pollution than any other wood- or pellet-burning appliance. They commonly reach a combustion efficiency of 90%. Masonry heaters include a firebox, a large masonry mass (such as bricks), and long twisting smoke channels that run through the masonry mass. A small hot fire built once or twice a day releases heated gases into the long masonry heat tunnels. The masonry absorbs the heat and then slowly releases it into the house over a period of 12–20 hours.
New high-efficiency wood stoves with catalytic combustors have advertised efficiencies of 70%–80%.
Modern fireplaces (which have vents under the firebox for drawing in room air, a heat exchanger, vents at the top of the fireplace for routing heated air, and a dedicated supply of outside air for combustion) provide benefits at efficiencies near those of woodstoves.
Before investing in a new wood-burning appliance, check with your local building codes department or state environmental agency about wood-burning restrictions.
If you have an older wood-burning appliance, consider upgrading to one of the newer >75% efficient appliances certified by the U.S. Environmental Protection Agency (EPA).