An outdoor wood-fired boiler furnace is an outside furnace that burns wood to heat water and transports that water via underground pipes into the home. It is typically shaped like a shed and houses a water tank and a wood-burning unit.
A wood-fired boiler furnace is safer to use than a petroleum or gas water heater, according to WoodFurnaces.net. The cost of running a wood-fired furnace is typically lower than that of traditional water heaters. Because of its small tank, this type of furnace keeps water hot for longer periods of time and conserves water because less of the liquid cycles through it.