The beauty and perceived warmth of a conventional wood fireplace comes with major caveats.A fireplace with an open front is is, at most, 10 percent efficient in converting wood to heat. Due to convection, heat is pulled out of a house through the chimney (chimney effect), bringing in cold air through cracks and unsealed areas. In addition, the masonry walls surrounding a fireplace have little insulation value, and further conduct the heat outward. Finally, a wood fireplace is positioned by exterior walls, which only worsens the overall heating efficiency. Dampers, flue sealers, glass doors and heat exchangers can increase fireplace efficiency. However, wood, pellet, and natural gas/propane fireplace inserts offer the most efficient alternatives.
Gas Fireplace Inserts
Gas fireplace inserts are fitted into existing fireplaces and offer a more energy-efficient alternative to wood-burning fireplaces. Gas or propane also burns more cleanly, and offers a continuous supply even during a power outage. Also, gas can be turned on or off instantly with a switch, leaving no ash or mess to deal with. However, retrofitting with a gas insert requires the installation of a new lining and an approved vent in the chimney. Also, only one type of fuel can be used in inserts; adapter kits are available to convert natural gas and propane inserts.
Vent-free Gas Inserts
Vent-free inserts are popular alternatives since they are inexpensive, simple to install and efficient. However, they use indoor air for combustion, and release the combustion gases back into the room. This causes the room’s oxygen levels to deplete, while adding carbon monoxide, and introducing water vapor as a byproduct. Manufacturers do not recommend these for homes that are tightly air-sealed, and also suggest no more than three hours of use per day.
Direct-vent, Sealed Combustion Gas Inserts
Direct-vent, sealed combustion inserts cost more, but are also higher-efficiency, making them by far the most efficient and safest option for gas fireplace inserts. These units strictly use outdoor air for combustion, and vent directly to the outside through the firebox, thus eliminating health and safety issues associated with the vent-free type.
Additional Features for Improved Efficiency
Depending on your budget, choose a direct-vent insert with a high-efficiency rating, as well as a unit that can be tied into your existing ductwork to distribute heat more evenly. Get a squirrel-cage circulating fan for quiet, efficient air circulation and ceramic glass doors for safety and effective heat transfer. You should also have a second heat exchanger to push more heat into a space, and variable settings to adjust the heat and fuel consumption.
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