Many companies manufacture wood-fired furnaces or boilers. The following list is not all inclusive, but does identify the major companies and shows how their products compare on the key indicators described below.
Wood-fired Furnace — produces hot air and is used with forced-air heating systems.
Wood-fired Hydronic Furnace* (wood boiler) — produces hot water and is used with hydronic radiant heating systems, forced-air heating systems, and other applications that use hot water.
Clean Burning — if you live in an area where smoke might be an irritant to neighbors, or where local agencies are enforcing emission standards or periodic "burn bans," you will want a unit that produces little or no smoke. All wood-fired devices produce smoke when cold-started, but clean burning units reach low emission levels in minutes.
Thermal Efficiency — thermal efficiency indicates how well the unit converts wood fuel into useable energy for home heating. High efficiency furnaces produce more heat per unit of fuel consumed, so they burn less wood and save you money over the long term. Clean burning wood furnaces are almost always high efficiency units too, which makes sense because they convert virtually all of the wood fuel into usable energy.
Safety Certified (UL and CSA) — safety certification means that a qualified independent laboratory has tested the furnace and certified that it complies with safety standards established by Underwriters Laboratory (UL 391-1955) and the Canadian Standards Association (CAN/CSA B366.1-M91). For your own protection, it makes sense to buy a unit that has been tested for safety. And if you plan to install the unit in your house or garage, you can be sure that your insurance company will insist on it.
The table below lists manufacturers of wood-fired boilers and furnaces with links to their websites. The comparative information represents information collected by Greenwood from the company's website and/or other information provided by the company**. We encourage you to do your own evaluation and decide which product or company will work best for you.
|Manufacturers||Air furnace||Hydronic Furnace/Boiler||Clean Burning||Thermal Efficiency||Safety Certified|
|Greenwood Clean Energy||3 models||Yes||85%||Yes|
|Tarm USA||-||6 models||Yes||80-85%||Yes|
|Alternate Heating Systems||-||8 models||Yes||85%||No|
|Hud-Son Products||-||3 models||No||No Claim||No|
|Central Boiler||-||5 models||No||No Claim||Yes|
|Free Heat Machine||-||3 models||No||No Claim||(1)|
|Gefco Hydronics||-||3 models||No||No Claim||No|
|Northwest Manufacturing||-||4 models||No||No Claim||No|
|The Wood Doctor||-||5 models||Yes||No Claim||Yes|
|Hardy Manufacturing||-||7 models||No||No Claim||Yes|
|Empyre||-||4 models||No||No Claim||Yes|
|Heatmor||-||6 models||No||No Claim||Yes|
|Mahoning||-||4 models||No||No Claim||No|
|Royall||3 models||3 models||No||No Claim||No|
|Kerr Heating||5 models||1 model||No||No Claim||No|
|Charmaster||6 models||-||No||No Claim||Yes|
|Valley Comfort / Blaze King||3 models||-||No||No Claim||Yes|
|Yukon Eagle||6 models||-||No||No Claim||Yes|
(1) Control panel is UL-listed.
(2) US distributor claims units are certified to UL 391-1955 and CSA B366.1-M91 but test lab name and report number have not been provided.
* "Hydronic furnace" is the term newly adopted by the American Society for Testing and Materials (ASTM) to more accurately describe devices called "wood boilers." Use of the term "boiler" led many people to believe the device was pressurized and produced steam for heating. In fact, most "wood boilers" operate under zero pressure and produce only hot water.
** For corrections or additions to information presented, email Greenwood's webmaster.