Wood furnaces are direct fire heaters. It is a convenient and economical way of heating homes. Many Americans, Europeans, Canadians and people from other countries who experience very cold weather or climate use this kind of unit.

Many users nowadays prefer using wood furnaces to save the Earth from greenhouse effect. Burning bio-mass fuels does not increase the risk of carbon dioxide in the atmosphere. Since wood is a renewable resource safe for the environment, it can also conserve energy.

There are three main types of wood furnaces. First is the Central Wood Furnaces. It can be installed inside the house, garage, mechanical room or at the basement. It uses either a type of forced-air or hot-water system to distribute heat throughout the house.

The second type is the Multi-Fuel Furnaces. This unit can be placed inside or outside the house. It enables the burning of different kinds of fuel like coal, oil, gas and wood. These types are flexible that can work as a back-up option, especially when using other kinds of fuel. It is appropriate in cases where there is only one chimney outlet available. The machine allows venting of the wood as well as the fossil fuel so as to exhaust-up the same pipe.

The third type is the Outdoor Furnace or Boilers. This unit utilizes firewood, particularly when there is a huge supply. It keeps the smoke, mess and bugs outside. The furnace is similar to a small utility building. It is a wood burning furnace placed outdoors. It can be found along the yard, between 50 and 150 feet away from the house.

The furnace firebox is surrounded by a water jacket. As heat is released, it is transferred from the fire onto the water. It is then pumped through insulated pipes and placed underground, then into your house. Finally, heat radiates to warm up the entire house.

On the downside, this unit needs some boots, gloves and a cap to slog out onto the blowing snow to keep it going. Many outdoor boilers are hard to control for a clean burn due to their oversized firebox. Aside from this, it tends to smoke a lot during automatic restart after a long off cycle.

All these wood furnaces are controlled by a thermostat similar to other heating systems. Different heating systems are used on working on these types.

The forced hot-air systems use heat exchangers. The warm air spreads out with ductwork. Burning fuel causes the heat exchanger to heat-up. However, there is no heat storage capacity in this system. The unit needs to be re-fueled everyday to maintain its temperature during the cold months. It is also easy to add filtration, air-conditioning and humidification because the air in this system is being re-circulated.

Hydro-air units use ductworks to help distribute air similar to forced hot-air systems. The heat exchanger is replaced by a hot water coil being heated by a hot water loop from its boiler. There are multiple hydro-air units that can be fed by a single boiler throughout the sections of the house for different cool zones. This kind of system is always combined with air-conditioning.

A combination central-heating unit system is designed to burn wood, oil or gas. It relies on the back-up fuel when the wood is not convenient for usage. Both combustion chambers can be maximized with this design. The two fuels are not usually used simultaneously. It can either be hot-air or hot-water furnaces. The disadvantage of this unit is that it tends to be twice as expensive as a single-fuel heater. This dual system offer maximum fueling flexibility.

Wood furnaces have disadvantages also. Some needs to be refueled several times and are a bit dirty to operate. It is also not always convenient to gather fire woods. And to produce good heat, you must know how to stack these pieces of wood properly. Lastly, all these units require electricity due to its thermostat.