Heating with wood is a great option for many households – and a must for most off-gridders and homesteaders. Wood stoves are easy to use and the feedstock is renewable and easy to obtain. If you live in a heavily wooded area, are living without electricity, or simply want to reduce your fuel bill, wood stoves often make a good deal of sense.
In this article, we are going to explore the different types of wood stoves, their features, and differing levels of efficiency. Not all wood stoves are created equal, and they can range from something as simple as a 50-gallon steel drum to something more complicated, like a circulating stove with a catalytic converter.
We’ll begin with one of the most iconic kinds of wood-burning heaters: the open fireplace. Open fireplaces are popular because they’re romantic and make a nice visual addition to a room. Who hasn’t imagined themselves relaxing at the hunting lounge with a big, stone fireplace in the center of the living room? The problem with open fireplaces is that they are extremely inefficient.
Why? Because they actually suck all the heat out of a room, sending it outside via the chimney. Because of this, you will rarely find fireplaces in homes where wood is the main source of heat. Not only are they hugely inefficient, but fireplaces are also extremely smoky. This is an annoyance, but it’s an indicator that you are not getting a very clean, and therefore efficient, burn of the wood itself. Modern fireplaces typically only covert 10 percent to 20 percent of wood burned to heat.
Radiant Heat Stove
Another common wood stove is a radiant heat-type wood stove. These wood stoves heat the area around them by radiating the heat from an enclosed chamber. Common types of radiant heat wood stoves include potbelly stoves and rocket mass heaters. Because the combustion chamber is either enclosed or insulated, radiant heat wood stoves will be much more efficient than an open burning fireplace, and the heat will be radiated into the room for a much longer time after the fire has gone out.
There are varying levels of efficiencies within radiant heat wood stoves, with perhaps the most efficient being a rocket mass heater. Rocket mass heaters use an insulated burn chamber, are designed for more draft, and have heat-exchange passages that capture exhaust gases before they escape through the chimney, resulting in a cleaner burn that can be up to eight times more efficient than traditional radiant heat wood stoves. The heat created from a rocket mass heater is then radiated into the room via a thermal mass (concrete, adobe, dirt, etc.) that surrounds the heating components.
Radiant heat wood stoves can be inexpensively built out of something as simple as a 55-gallon steel drum with a chimney attached. Although this can be a great option if you have the materials lying around or can procure them cheaply, keep in the mind that the life of these wood stoves will be much less than something built out of sturdier material like firebrick, concrete or cast iron.
Circulating Heat Stove
The more modern kind of wood stoves that you can purchase at many heating supply stores are circulating stoves that use air to heat the living space. Circulating stoves are double walled with an inner combustion chamber. There is an air space between the two walls where air is passed over the inner wall near the combustion chamber, and then pushed out into the room, conveying heat. These types of stoves can achieve 70 percent to 80 percent efficiencies and are popular for families with children, since the outer wall of the stove does not get nearly as hot as with radiant-type stoves.
As air pollution became more and more of a concern, many circulating wood stoves started to integrate catalytic converters and secondary air combustion chambers to reduce emissions and increase efficiency. Catalytic converters are simply platinum grids that are placed in the firebox of the stoves, capturing the exhaust and combusting it for a cleaner burn. Modern circulating stoves that do not have catalytic converters have a damper that directs smoke from the stove into a secondary chamber, where hot air is added and reignites any unburned fuel.
Non-catalytic circulating stoves are often cheaper than catalytic stoves and easier to maintain. A wood stove with a catalytic converter is more efficient than one without, but the catalytic converter will need to be replaced every five years and may require yearly maintenance.
Wood stoves are a great way to reduce you heating bill, reduce your reliance on the electric grid and make use of a renewable natural resource. When choosing one, take into consideration your budget, the size of space you want to heat and your desired efficiency for a warm, happy home.
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