Author – Todd Woofenden
Since there are countless different stove models in the field, each with its unique characteristics, it is beyond the scope of this book to cover the fine points of wood stove operation. But here are some general tips for all wood burners.
Tip #1: Read the owner’s manual
For starters, if you have the owner’s manual, read it. There is bound to be lots of useful information about the features of your model, and how to use the stove to its full potential.
If you don’t have a manual, ask at your local stove shop. If the stove’s not too old, you might be able to buy a manual for it. Look for a label on the back of the stove with the model name/number and other identifying information.
Tip #2: Use the right fuel
Use seasoned hardwood for fuel. Seasoned wood is wood that has been stored under cover for the better part of a year. Season your wood under cover, but with good air flow. If you use a tarp to cover the stack, just cover the top. Leave the sides of the stack open.
Why does it have to be seasoned?
In short, because “green” or wet wood doesn’t burn well. Here’s why: Water has a high specific heat.
Specific heat: The amount of heat required to raise one gram of a substance by one degree Celsius.
Since water has a high specific heat, it takes a lot of heat to boil the water away, leaving less heat to keep the combustion process going efficiently. The ideal moisture content of seasoned firewood is about 20% to 25%. Fresh cut (“green”) wood usually has a moisture content of 35% to 70%.
Why not burn soft woods?
Although soft woods like pine or white spruce will burn (if seasoned), they have a lower BTU content than hard woods, like oak and maple.
A BTU is a “British Thermal Unit,” the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.
Primarily because of their higher BTU content, hardwoods tend to offer a longer burn time and more even heat. But especially with the “airtight” generation of wood stoves, there is another reason: soft woods tend to dry more quickly than hardwoods, and when dry, tend to burn very hot and fast. This causes the wood stove user to damp the stove down more than usual, to prevent over-firing. Since rapid burning means that lots of combustible gasses are being emitted from the fuel load all at once, reducing the air intake means there is not likely to be enough oxygen to burn all the combustible gasses. Fuel is wasted in the form of unburned smoke.
So although these lower-quality soft woods will often burn acceptably in an open fireplace where regulating the air intake isn’t an issue, wood stoves require better fuel for proper operation.
How about super-dry wood?
Seasoned wood burns better than green wood. So won’t super-dry wood burn even better? For wood stove use, no, for much the same reason that soft woods aren’t ideal:
When wood is too dry – even good hard wood – combustible gasses are emitted too quickly in the burning process. The fire burns fast and furious, forcing the stove user to damp the stove down.
In an “airtight” stove this leads to a smoky fire, since there is not enough air entering the stove for complete combustion. And that means wasted fuel in the form of unburned smoke, greater creosote buildup in the flue, and more pollution.
In a non-cat EPA-certified stove, the secondary phase of combustion won’t be able to keep up with the rapid flow of combustible gasses, and the result will be similar: wasted fuel and more deposits in the flue In a catalytic stove, the catalytic unit can actually overheat, causing damage to the unit. And there is another possible problem with all three types of stoves: backpuffing.
Backpuffing: Jets of smoke emitted from a wood stove, caused by the ignition of a buildup of combustible gasses in the firebox.
Backpuffing is essentially small explosions in the stove, forcing puffs of smoke into the room through every available gap in the stove or stovepipe. It is caused by a combination of reduced airflow into the stove and use of too-dry wood or wood that’s split so small that it burns too rapidly. Instead of the gasses burning as they are emitted, they collect in the firebox. Oxygen slowly enters the firebox, and when there is finally enough, the gasses ignite.
The problem of backpuffing is also a good reason not to burn things like kiln- dried wood blocks, pallets, and trimmings from wood shops, except as kindling.
Tip #3: Learn the right way to build a fire
If you are not a seasoned firebuilder, see article “How to Build a Fire.” In a wood stove, the trick is to use enough kindling and small splits of wood to establish a bed of coals quickly, then to add larger logs.
~ Todd Woofenden