Wood Stoves

Wood-burning stoves are a much less significant problem than open burning, outdoor wood-fired boilers or even fireplaces.  Wood stoves burn fuel much more economically, some times reaching 90% efficiency.  Higher flues and chimney stacks release these emissions higher in the air, reducing their impact on breathable air than open burning or outdoor wood-fired boilers, but they still produce high levels of emissions and particulate matter that can impact local air quality.

Wood can also present significant issues when used as the primary fuel to heat a home.  Wood brought in from outside the local area can transport pests that can damage everything from forests to apple orchards.  Homeowners might not always properly dry their wood before use, producing large amounts of smoke but little heat.  Wood is also not as “green” of a fuel source as people commonly think. While wood from trees that have died naturally can be carbon neutral, any wood coming from harvested trees produces extra carbon that would not otherwise be in the atmosphere.  These emissions contribute to the net rise in CO2 that is causing global climate change.

It is important to use an EPA-certified wood-stove if you choose to heat your home with wood. These stoves are cleaner-burning and consume less fuel than older, uncertified models, producing only 2 to 7 grams of smoke per hour, as opposed 15 to 30 grams from older models. Be sure to purchase a stove that is the correct size of the room or building that you will be heating. Larger stoves will emit more emissions and can make the building uncomfortable, while smaller stoves will be inefficient at heating the space and will need to operate more frequently. The EPA advises consumers consult with a professional when deciding how large of a wood stove to buy to ensure they choose the right one.

Three types of wood stoves meet EPA standards: non-catalytic, catalytic, and pellet stoves. Non-catalytic stoves are simpler in design and easier to operate but are generally less efficient. Catalytic stoves have a ceramic element through which the smoke passes, helping them produce a more even heat while reducing emissions. Pellet stoves are the most efficient and cleanest burning EPA Certified stoves, but they require a unique fuel consisting of compressed, pelletized biomass, and cannot use regular wood.[i]

Wood stoves can also be improved by adding a thermal mass, such as concrete or soap stone, to store and radiate heat.[ii]  These stoves often require smaller and less frequent fires because the thermal mass stores heat and radiates it over a long period of time.  Stoves with thermal mass can also use off-peak electricity as a supplemental heating source if they incorporate electric rods.[iii]  The weight of these stoves, however, requires special re-enforcement of foundations and flooring to support, making them a significant financial investment.

One of the most important aspects of operating a wood stove is choosing correct fuel.  Try and only use wood from trees that died naturally, or that were blown-over in a storm.  Select wood from your local area, and keep it outside and away from the house to minimize pest problems.[iv] Make sure the wood has had time to dry properly before burning.  Use a shed or tarp to cover wood after it has been cut to prevent it from absorbing new moisture.  Only bring your wood inside when you are ready to burn.

For more information on wood stoves, check out the EPA’s FAQ on certified wood stoves. For a list of wood stoves approved by the EPA (as of December 2013), click here (pdf).

Wood stoves (and fireplaces) should NEVER be used to burn garbage.

Source: http://www.epa.gov/burnwise/woodstoves.html

[i] Wood pellets also contain a significant amount of embodied energy due to their production process.  This energy reduces the overall efficiency of pellets as a heating source.

[ii] Normal wood stoves only heat the air in the room, which can lose heat quickly after the fire goes out.  Heating a thermal mass helps to retain the heat for a longer time with a smaller amount of fuel.

[iii] Incorporating electric rods offers an alternative way to heat the thermal mass of the stove.

[iv] If you cannot source your wood from your own property, try and work with a near-by farm to source your wood sustainably.

2 thoughts on “Wood Stoves

  1. EPA approved wood stoves are not the answer in residential areas. In Libby Montana there was an almost complete change out with minimal improvement. http://woodsmoke.3sc.net/ahha-tactics/Libby_change_out_Brauer.png The American EPA standards are now being changed as the current stove standards are far to toxic. The World Health Organization recently announced Particulate Matter to be Carcinogenic which as you know wood stove emissions are mainly comprised of. The cities of Hamstead Quebec and Montreal have and are about to ban wood stoves entirely. I just recently was instrumental in getting the Canadian Medical Association to adopt a resolution to educate the public on the health hazards of wood smoke.

  2. The fact that a stove meets EPA emission standards does not mean that the emissions are not a threat to neighbors. A wood stove meeting EPA standards of , say 4 grams/hour is polluting the equivalent of 24 cars—-not a great situation for neighbors. As far as the city, as a whole, auto pollution is a health concern so increasing this level 24 fold is alarming. Not that wood stoves meet EPA standards in the real World. The threat many cities now face are the emissions from Outdoor Wood Boilers with emissions ten to twenty times that of a wood stove.

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