Literally dozens of kinds of wood burning stoves are available. Most can be described by one of the following general categories. These are double walled with an inner combustion chamber usually constructed of cast iron or firebrick-lined welded steel. An outer shell of lightweight sheet metal promotes the flow of air over the inner shell. The room is heated primarily by warm air.
Some units have an optional fan, which provides a more positive air flow.
You obtain draft control and heat output with a damper operated by a thermostat. Burning efficiencies of 60 to 70 percent are possible with well-built units. The major advantage of the circulating unit is that during operation, the outer shell stays relatively cool. These single walled units may be constructed of sheet metal, cast iron or welded steel. They may or may not be lined with firebrick, which improves the stove's efficiency and prolongs its life.