Outdoor wood furnaces aren't for everybody. They have a niche in the central heating market, but they fill that niche well. If the circumstances are right, few heating options provide a more efficient, dependable, and comprehensive heating source. The drawbacks are simple enough. You need to have a reasonably convenient source of wood and you need to have a viable place to put the furnace installation. Obviously, this lends itself to more rural homes, but you don't need to live in the middle of nowhere or in a heavily wooded area to make this a viable heating option.
Advantages of an Outdoor Wood Furnace
Choosing an outdoor wood burning furnace will give you immediate and long term benefits. You can eliminate most of your utility bill for your home. That's always nice. Several heating options can save you a lot on your monthly bills, though. An outdoor wood furnace can heat several buildings at once, including a stand alone garage, a shed, or—with a higher-rated furnace and good insulation—multiple homes. Not too many heating systems can say that.
Another good bonus for moving your heating source outside is that it eliminates one more fire hazard from your home. For even better safety, make sure you choose a model that has fail-safes for pressure, loss of electricity, and flash burning. A good outdoor wood furnace should be safer than many other heating sources, but a low-end furnace can expose you to unnecessary risks.
Make an Investment
An outdoor wood burning furnace isn't an installation you want to skimp on. Performance between models and companies can vary greatly. Different designs are better for efficiency, others are better for producing greater amounts of heat. The outdoor structure of the furnace must provide its own insulation and less-efficient features will show immense heat loss given the furnace is among the elements. Dozens of factors determine overall performance, but the furnace door and a good exhaust system are paramount.
You should also make an investment to ensure your home has a good overall insulation rating, but probably not for the reason you think. An outdoor wood furnace is an efficient way of heating your home, regardless, but good insulation will reduce the time you spend gathering wood and feeding it to the furnace. A well-insulated home with a high-rated outdoor furnace will keep this task from getting tedious. If you really want a premium heating system, radiant flooring will also help your outdoor wood burning furnace go a long way.
Longevity and Maintenance
Again, the quality of your furnace will vary greatly on your model and this includes its longevity. A low-end, poorly maintained furnace may last less than ten years. On the other hand, a high-end, properly maintained furnace can last indefinitely. Periodic inspections and the occasional cleaning will ensure your furnace is operating as it should. Keeping the furnace free from rust and creosote (a wood burning by product) are the most important things for proper maintenance.
This is an excerpt from THE book "Off the Grid" and provides the base idea how to build an outdoor wood furnace.
One of the problems we have with smaller off-grid cabins is the commercial wood stoves are too big, throw off too much heat and require too much clearance.
If you get a real small stove you end up having to refill it several times to keep your cabins warm through the day.
So I came up with this simple design that uses an inexpensive steel barrel and a cheap Vogelzang wood stove kit that will hold a much larger fire for keeping your cabin warm but is placed outside so it doesn't take up room in the cabin. Can also be used for heating water and even baking and cooking with some racks attached to the walls and a tank with lines run into the cabin.
The outdoor furnace ha two vents one at top and bottom. The colder air will be pulled in through the lower vent and heated and heated air is pushed out of the top vent into the house. no fan is needed but could be attached at the top vent.
I would suggest using steel 2x4s and sheet metal for the sides and roof and a cement or patio block pad floor. You do need a vent in the door for the stove to get adequate air and a damper in the flue pipe.
You should be able to find all the building materials locally and you can get the Vogelzang barrel stove kit and accessories at http://vogelzang.com
