Controlled combustion "airtight" stoves and furnaces have been available commercially since the 1970's; much-reduced emissions stoves and pellet/corn stoves since the late-1980's.
All are mature technologies in different stages of technical evolution. Stoves are nearing the end of a second generation. Furnaces and boilers are just entering a second generation. Pellet and corn stoves are at the end of first generation. Specific "high temperature" pre-fab chimneys are required for wood burning appliances.
Installation requires abilities within reach of persons familiar with construction/renovation, provided they become thoroughly familiar with installation requirements and do not face a challenging installation. However, in most cases, insurance companies would prefer installation by a WETT (Wood Energy Technology Transfer)-certified installer. Ensuring a safe installation requires a thorough inspection by a person knowledgeable in the area and/or professional installation, WETT-certified. Normal operation by persons with no or limited training can be possible by following the manufacturer's instructions.
Firewood fuelled units normally require refuelling every 3 - 8 hours of operation, pellet stoves twice a day to once every few days, depending on the size of their hopper. Venting systems typically require cleaning 1 - 2 times per year. Maintenance typically involves periodic ash removal, a seasonal inspection, occasional replacement of gaskets and high temperature components such as baffles and catalytic converters. Because of poorer combustion, furnaces and boilers tend to have much higher emissions and generally require more frequent chimney inspection and cleaning.
Stoves are available in sizes ranging from room heaters to units intended to provide enough heat for a typical home. Furnaces can heat a medium to large home, and units intended for small commercial applications are readily available.
From less than 20 MJ/h to over 200MJ/h
Stoves heat adjacent areas by radiation and convection as well as heating the room air, sometimes assisted by fans. Furnaces heat the building air by means of a circulating ducted system. Boilers provide hot water as the heat transfer medium through a system of pipes and radiators/convectors.
Typical 50 to 120 $/MJ
Stoves and furnaces/boilers may be restricted in their installation or use in a few areas to ensure safe and efficient operation. They will produce excessive smoke and pose a fire hazard if improperly operated or maintained. Delivered efficiency of wood fired furnaces and boilers is generally lower than stoves, due to the losses associated with generating heat in an area remote from its usage.
All systems may require occasional replacement of insulation and baffles in high temperature areas.
All these units should have a virtually unlimited life expectancy, with occasional replacement of components. Pellet stoves have experienced increased reliability issues in the past due to their added complexity and lack of long-term operating experience, and variation in fuel quality.
The Hearth Patio Barbecue Association is the international association of many manufacturers of these products. Their website includes links to members, and is found at www.hpba.org.