After almost thirty years of telling people to burn only dry wood and not to let their fires smolder, we should admit that such general instructions don’t work very well. I speak from experience, having co-authored the following statements decades ago in a booklet that was widely distributed.
“Match the size of the fire to the heating needs of the home. When the weather is mild, avoid filling the firebox to capacity; rather, build a small compact fire and load the appliance more often. . . Use dry wood. The moisture content of the wood has a large effect on the ability of your appliance to make heat. . . Never let the fire smolder. Think of wood smoke as wasted energy and operate the stove in such a way as to use it before it enters the flue pipe.”
The Billpayer’s Guide to Heating Systems Energy, Mines and Resources Canada 1983
Here is a recent statement from an authoritative source:
“Engaging the public and giving them the tools to make the right decisions about what they burn and how they burn is the first step in an overall wood smoke plan. With proper burning techniques and well-seasoned wood, emissions (even in older stoves) can be significantly reduced.”
Strategies for Reducing Residential Wood Smoke U.S. EPA October 29, 2009
We at woodheat.org agree wholeheartedly, but the problem is that engaging the public is not easy. An experienced educator will tell you that teaching anything to adults is a challenge. Well, actually, the teaching is easy. The tricky part is getting the adult to learn. The educator might also say that the only meaningful evidence that learning has happened is a change in the learner’s behavior.
So those of us whose objective is to reduce wood smoke emissions through public education have our work cut out for us. First, it is hard to get adults to learn something, and second, our main goal is not just for them to listen but to get them to change their behavior. If we fail to achieve that goal, we will have wasted our time and resources.
The trouble with adults is that we get stuck in particular ways of doing and thinking about things. A repetitive task like loading a wood stove can become so routine that no thought goes into it, and that is a problem because thoughtless wood burners make a lot of smoke.
This is from our report on a series of Burn it Smart workshops delivered in 2004 (pdf warning 900KB).
“Wood burners can be a prickly lot, and breaking through that kind of resistance to promote behavioral change was to be our challenge. While many, if not most, people who heat with wood claim to have confidence in their skills, I see evidence of an underlying uncertainty related to the private, often solitary nature of the practice of wood burning, and that this gives rise to a thirst for information, if only the desire for confirmation that they are on the right track. The key is to find a way around the outward confidence and past the resistance to tap into that underlying uncertainty.”
Everyone who attempts to communicate with the public about wood smoke tells people to burn hot and not let their fires smolder. The problem is that without giving specific instructions on how to achieve these goals, people are likely to keep doing what they do now, which often includes smoky fires. And yet a review of even the most recent public information efforts aimed at reducing smoke reveals the same old general instructions, the very ones that haven’t worked after all these years.
At woodheat.org we respond to between two and three thousand questions by email each year, and there are a couple of thousand more messages posted to our
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discussion list annually. After years of reading thousands of comments and questions from regular wood heat users, one begins to see patterns in the way people think about their wood heating practice.
We have collected and refined a series of messages that do seem to have met with some success. I should stress, however, that there is no empirical evidence that people’s behavior changed or that the apparent change was permanent. But plenty of people have said they learned something at a workshop or read about it on our site years ago, and it changed their wood heating practice permanently. We’ll have to take their word for it.
Below is a list of operating suggestions presented in their briefest form, just to illustrate the amount of detail that we have found works best. Obviously, every person who is exposed to such a list will not act on them all, but it seems like they only need to try one or two that produce a benefit and that experience can lead to other changes in practice. Some of these suggestions are specific to the most common combustion system configuration, which is the EPA certified updraft horizontal baffle design. Other combustion options such as catalytic, downdraft, sidedraft, and masonry heaters have specific operating procedures. However the objectives implied by all of the techniques are applicable to all appliance types.
Two reasons why people are tempted to smolder wood fires:
First, they are reluctant to burn the appliance hot enough because they are worried about overheating nearby combustibles. Our response is that you can’t burn clean if you fear for your safety because the installation doesn’t conform to code requirements. So the first step is to get it inspected and brought into code compliance.
And second, they think that all the heat that goes up the chimney is wasted heat so they concentrate on keeping the flue gas temperature down. We say that about 20% of the heat released by the burning fuel must be given to the chimney to keep it clean and working properly. It is more efficient to burn the smoke and give plenty of heat to the chimney, than to waste the energy in the smoke by smoldering.
Two reasons why people often burn wet wood:
Procrastination and wishful thinking, and most of us have been guilty of both at one time or other. Firewood dries very slowly, and the harder the wood, the slower it dries. The wetter the climate the slower wood dries. The more shaded the location, the slower wood dries. It has become clear that the super hardwoods like oak and maple will not dry sufficiently in just the summer months. These are difficult lessons to learn.
Five ways to tell if firewood is dry enough:
1. It darkens with age and sun exposure
2. Cracks or checks form in the end grain
3. Two pieces of seasoned wood sound hollow when knocked together
4. A freshly split surface feels warm and dry
5. It does not hiss or bubble from the end grain when burned.
For most users a wood moisture meter is a waste of money because they can be expensive and only tend to be used a few times.
Some other suggestions:
Many people find that starting their fires top down is more reliable and smoke-free than the conventional bottom up approach.
Most commercial firewood is not split small enough. A range of piece sizes is best for convenient stoking, and for home heaters, no piece should be bigger than about six inches in cross section. The smaller the appliance firebox, the smaller the pieces should be. The lower the house heat demand, such as in fall and spring, the smaller the pieces should be.
Ashes should be removed from the firebox frequently so they don’t interfere with good stoking technique. The advice to leave an inch of ash in the firebox, although commonly heard, is deeply counterproductive because all that ash interferes with effective stoking. The best time to remove ash is after an overnight burn before the coals are raked.
Rake the hot coals towards the air inlet before loading to achieve quick ignition. Put the smallest piece of firewood on the coals as the igniter.
Never add just one piece of wood at a time in the attempt to produce a steady heat output. Wood burns best in cycles. Load at least three pieces, and preferably more, each time the heater is loaded.
Open the air control fully and let the fuel burn until the firebox is full of flames, the edges of pieces are glowing and a layer of char has formed on them.
In starting a fire or rekindling from coals, the objectives are to heat up the chimney so it produces strong draft, and heat up all parts of the firebox so clean combustion can be sustained when the air supply is reduced for an extended burn.
Reduce the air control setting gradually in two or three steps to avoid shocking the fire and extinguishing the flames.
Each load should flame brightly until it is reduced to charcoal.
When the heating load is low, as it is in spring and fall, load in a crisscross configuration for a quick fire to take the chill off. In mild weather it is better to let the fire go out and build a new fire once a day than to smolder fires continuously.
In cold weather you can build tightly packed fuel loads, provided the wood flames brightly until it is reduced to charcoal.
Five ways to control heat output in mild weather:
1. Use a lighter wood like poplar, willow, spruce or pine
2. Build smaller fires, not with fewer pieces, but with smaller pieces
3. Load in a crisscross configuration
4. Load east-west (if you can)
5. Reduce the combustion air control setting.
Visual cues — If you are burning efficient fires, this is what you should see:
When wood burns it should be flaming until only charcoal remains. If there are no flames, something is wrong.
If there are firebricks in the firebox, they should be tan in color, never black.
Steel or cast iron parts in the firebox should be light to dark brown, never black and shiny.
With proper size, seasoned wood, correct air settings, coal bed raking and proper loading arrangement you should expect almost instant ignition of a new load of wood.
If the appliance has a glass door with airwash, it should be clear.
If the appliance has a glass door without airwash, it will be hazy, but should never be totally black.
With an EPA certified appliance the exhaust at the top of the chimney should be clear once the fire is established. With a conventional appliance, the exhaust may be visible, but should never be dense or opaque.
The preceding list of suggestions is a sample of those that have been assembled slowly over many years. It is not comprehensive and has been presented in its briefest form to give a flavor of the level of detail we have found works best. I am not aware of any credible test program that has investigated the effectiveness of any of these techniques. The problem, therefore, is that the entire list can be easily dismissed as just somebody’s opinion. As anyone who has worked in residential wood heating for any length of time can attest, there is no shortage of opinion about all things wood burning.
Although we at woodheat.org have been working away at emissions reduction through public information for many years, we have never been supported or engaged to research, develop and refine the kinds of messages that are shown to be effective, and we are not aware of any other group that has done this kind of work. As a result, our view is that the entire field of emissions reduction through public education remains in its infancy.
The need for better educational strategies is real, as illustrated by a Feb. 17, 2010 article on the K2UU web site in Fairbanks, AK:
The Cold Climate Housing Research Center has been involved in studies of wood stoves and wood burning for the last three years. Researchers found that even EPA-approved stoves will pollute if not used properly.
Davies says the next project on the center’s wish list is to go inside people’s homes.
“There is no good information to know how people really burn their wood, so that’s one thing that we really want to get at,” he said.
This article started with a quote from the EPA stating that public information “is the first step in an overall wood smoke plan”. Obviously we agree with EPA staff in this matter, but our concern is that the real challenges of reaching people with messages they will act upon by changing their wood heating behaviors have been consistently under-estimated by just about everyone.
EPA has recently revamped and re-branded their wood heat web site as Burn Wise, and engaged with state and local partners with renewed vigor. It has also re-opened a discussion of the New Source Performance Standard for wood burning appliances in the hopes of refining and expanding its provisions. Along with these good steps, we suggest that the agency apply some resources to research and development of techniques and messages that can be shown to actually reduce emissions. The amount of public and private funding for wood heat-related public education has always been limited, so none of it should be wasted. We can no longer afford to go through the motions of public education by re-using the same old messages and hoping for a better result.
Although we are based in Canada, we have little to say about our federal government’s efforts to support responsible wood burning. Since their involvement with the Burn it Smart campaign wound down in 2005, the Canadian government has been missing in action. Still, we remain ready to partner with any government agency or private sector group that wants to help the public to burn wood better.
