Since 1988 new woodstoves have had to meet federal regulations regarding efficiency and pollution production - resulting in “EPA Approved” stoves that use a variety of methods to lower emissions and increase efficiency. These stoves use advanced design, catalytic combustors, and re-burners to “burn-off” the smoke produced by the initial combustion of wood.
Smoke is wasted fuel from a wood fire - in fact a cleanly burning EPA Approved woodstove operating correctly will give off little more than a transparent vapor cloud - with no real amount of smoke escaping the stove. That’s because the smoke itself is burned within the stove - resulting in better efficiency and greater heat output from the same amount of wood.
The BEST method to increase your woodburning efficiency is to get rid of your old, smokey insert or freestanding woodstove, and properly install one of these newer stoves.
Besides a re-vamp on your appliance, there are a few other things you can do to produce hotter fires, which produce less creosote and smoke, and burn more cleanly with greater heat output.
The single most important factor is the dryness of your firewood. Seasoned firewood contains much less water than “green” firewood - so the fire doesn’t waste it’s energy steaming off the water content, and more heat is available for complete combustion of the smoke. (See FeN #003 about firewood seasoning tips.) Seasoned firewood is easier to start, and will help keep the stove temperatures hot - to lessen the amount of smoke released up the connector pipe.
Another important part of efficient woodburning is to allow plenty of combustion air to enter the stove. Become familiar with the air inlets on your stove - this is usually the best area of the stove to ignite the kindling when first starting your fire. Once the fire is started, give it plenty of air for 15 to 30 minutes - allowing the stove and wood to heat-up and a bed of coals to start forming.
For hot “flash-fires” - intended to give off lower heat levels over several hours - load your stove in a small stack, loose criss-cross fashion, leaving plenty of space for air to flow into and around the stack. You want to get the fire hot and bright. Cut back on the air inlets as the fire progresses - but never enough to smolder the flames. When you have a hot bed of glowing coals, cut the air back enough to keep them hot and radiating heat. Repeat this process as needed to keep the house at the temperature you feel is comfortable.
For extended heating, and when you want to maximize heat output - start your fire like you would the flash fire - and when you get down to a hot bed of coals, load plenty of wood on the sides and on top of the bed of coals, concentrating the heat in a “pocket” of fresh firewood. This will sustain the fire and maximize heat output. Add wood around and over the “pocket” as needed to keep the heat concentrated.
To get a longer-lasting fires - burn your wood from the top-down. This is an ancient method of woodburning in Europe and is “catching on” here in the States. Basically you build your fire up-side down, with the split log base, working progressively smaller sections of firewood in a criss-cross manner to the top where you put you kindling. The only problem is that it’s less common to find the finely split wood needed for the center section of the stack - in America we just cut and split into large sections. Some experienced woodburners are finding the top-down method of burning is much more efficient, with long-lasting burns - a 18 inch stack can burn hot up to 4 hours without needing to be refueled.
Following these simple tips can help increase the efficiency of your woodstove or fireplace, decrease emissions, and warm you longer.