Outdoor Wood Furnaces – How To Buy A Wood Burning Furnace
In Canada and other extreme winter regions of North America, outdoor wood furnaces are becoming very popular. In essence, an outdoor wood furnace is a type of wood burning boiler that heats up water or air to be used in either a hydronic (liquid-based) or forced-air heating system for a house or building. Most modern outdoor wood furnaces are used to create hot water for circulation in some type of whole house hydronic system. The hot water flows from the outdoor wood furnace through an underground pipe and into either through baseboard “radiators” or wall panels or an in-floor radiant heating zone.
If properly setup, an outdoor boiler can also warm up for water for domestic uses like bathing, washing and cooking. But the key to successful use of wood fired furnaces is a ready access to either wood or pellets (combustible fuel capsules made from wood, corn, etc.) Externally, outdoor wood furnaces are housed inside small metal sheds or buildings, usually on top of fire resistant pads such as a concrete slab, cinder blocks or gravel and stone. Internally they are comprised of several major components or furnace parts: a water storage unit, a combustion chamber with firebox, a blower fan, dampers, chimney and access doors for loading the fire and cleaning out ashes.
The basic configuration changes depending on the wood boiler designers, fuel sources and number of heating units or BTUs they are supposed to release. But all types of outdoor wood furnaces have certain things in common that you should consider before buying one.
Concern #1:
It takes a lot of work to run one of these units; real honest to gosh, old fashioned, muscle-straining work. Even if you are able to buy your firewood or pellets in bulk, you still have to manually store the fuel, load it in the boiler and keep it loaded several times a day depending on the weather. If you can’t imagine yourself slugging though the snow to the wood pile or shed, carrying armload after armload of wood or shoveling 20 to 100 pounds or kilos of pellets every single day to feed the furnace then you can stop thinking about owning one right now. But if you and your family is prepared and committed for the sheer physical effort involved then read on.
Concern #2:
It takes a lot of storage space. It takes a lot of room to store firewood or pellets to heat a normal-size house with all its hot water needs for an entire winter. More than most people think. For example cordwood or firewood is sold in “cords”. In the US, a cord is a measurement of 128 cubic feet or pile of wood stacked 4ft high by 4ft wide by 8 ft long. An average cord of wood can weigh about 5600 lbs (give or take for moisture).
And an average home can easily burn through 4 to 7 cords of dry hardwood, more if you use wet wood or quicker burning softwood like pine or fir. That is just under 20 tons of wood that covers over 244 square feet! That is almost the same space as you would have in two average sized rooms. Two rooms stacked completely with wood four feet high! Now imagine those same two rooms filled with compressed wood or corn pellets. Smaller and lighter granted but still completely full with 3 to 4 tons worth, that you must move by the shovel load.
As mentioned before outdoor wood furnaces are not for everyone but if you have the access to the fuel and willing to commit to the time and effort involved you can save a lot of money on winter heating bills.
