Fireplace Efficiency Calculator

How It Works

An open fireplace is one of the least efficient ways to heat a home. Only about 10 percent of the heat from burning wood actually enters the room — the other 90 percent goes up the chimney along with warm indoor air that gets pulled in as replacement. In fact, an open fireplace can make your home colder by pulling more heated air out than it puts in. A fireplace insert dramatically improves this to around 65 percent by containing the fire in a sealed firebox with a heat exchanger. EPA-certified wood stoves reach 75 percent efficiency or higher. Gas vent-free units approach 99 percent because all combustion gases stay inside, though they require adequate room ventilation.