Wood-fired Central Heat

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By Greg Pahl

If you want to heat your home with wood, should you choose a woodburning furnace or boiler rather than a woodstove? Woodstoves generally cost less and have better overall efficiency and lower emissions, but sometimes stoves just aren't practical as the sole heat source in homes with many rooms. Some people also prefer a furnace to keep the associated mess or potential hazard out of the main living space.

Central wood heaters and boilers, normally installed in the basement or a utility room, distribute their heat with forcedhot-air or circulating hot-water systems, and can heat any home. If you have a ready supply of firewood and you enjoy handling wood, a wood furnace or boiler may be a good choice.

"There have been substantial changes in the last 10 to 20 years that make it easier and more convenient to use woodfired central heat," according to Lloyd Nichols, co-owner of boiler distributor TARM USA, Inc. in Lyme, New Hampshire. "Part of that equation is that homes have become less energy demanding. Couple that with a more efficient, cleaner-burning heater and the results are impressive. Now, instead of using eight to 10 cords to heat a typical home, we're talking between two to five cords."

The best modern wood-fired furnaces are designed to achieve extremely hot fires that create a lot of usable heat and leave little in the way of emissions to go up the stack. Except for the handling of the firewood, these heaters tend to function more or less like their oil- or gas-fired competitors and are generally controlled by a standard thermostat. When your home is warm enough, the thermostat causes the damper to close, and the fire burns at a reduced level. When more heat is called for, the damper automatically opens again and the fire comes back to a higher temperature.

FORCED-HOT-AIR SYSTEMS

If your home already has forced-hot-air ductwork, you may want to consider installing a wood-fired furnace (as opposed to a hydronic hot water system). These furnaces generally are thermostatically controlled, have a good-sized firebox, automatic draft control and optional hotwater coils. Many wood furnaces also are designed to burn coal, and some have blowers for increased combustion temperatures as well as optional evaporation pans for humidification. Regardless of their individual features, they all burn wood to heat the air in a heat exchanger. The heated air then is distributed to the living space in your home through ductwork. Because there is generally no heat storage capacity in a forced-hot-air system, the furnace needs to be refueled regularly in order to maintain a comfortable temperature in your home during the colder winter months. This can be a problem for people who are away from home for extended periods of time or who have irregular or unpredictable schedules during the winter.