Wood is Good Again
A growing awareness of the environmental impact of fossil fuels (such as natural gas, oil and coal) along with the desire to be more energy independent have encouraged a renewed interest in heating with wood. Not too long ago, even the best wood stoves weren’t terribly efficient. In fact, the haze they produced was a sign that homeowners’ hard earned heating money was literally going up in smoke. A lot has changed since 1990. That was when the United States Environmental Protection Agency (EPA) mandated strict particle emissions standards for stove manufacturers. Today, all new wood stoves are EPA-certified. And that means they are much more efficient, and friendlier to the environment as well. But doesn’t burning wood produce pollutants just like coal or oil? Well, the answer is yes…and no. When fossil fuels are taken out of the earth and burned, they produce an overload of carbon dioxide in the atmosphere. And since these fuels are produced far from where they will ultimately be consumed, mishaps such as oil spills cause other problems. Once burned, fossil fuels are gone forever. Wood is different. As all plants grow, they absorb carbon dioxide from the air and convert it to fiber. The carbon dioxide is released after they die, whether they are burned, or simply left to rot in the forest. This process is part of nature’s cycle. Heating with wood can be both satisfying and economical. But it requires special care right from the beginning.
Which Wood Stove is right for me?
When choosing a wood stove, there’s a lot to consider. Start by locating the sticker pictured on this page. It will tell you that the stove is EPA- certified (a permanent notice is also on the back of the stove). It will also tell you the Btu rating. This is a measure of heat output which will help you find a stove
This information that supplies an adequate amount of heat where you want it and no more. One common error people sometimes make is to purchase too powerful a stove for their home. An oversized stove is a potential fire hazard, because it’s often operated in an extremely “slow fired” condition, which leads to creosote buildup. And that increases the risk of chimney fires. So before you go stove shopping, ask yourself two questions. How much heat should it supply enough for one room, or the whole house? Where do you want to install it? Common types of woodburning appliances are free- standing wood stoves, fireplaces, and fireplace inserts. And besides the living room or family room, these days they’re likely to be chugging away in bedrooms, kitchens, and even bathrooms.
“Cat” and “non-cat” - two different breeds.
This refers to the two methods employed in new stoves to keep them running clean and efficiently. “Cats” use catalytic combustors, and “noncats” recirculate the smoke and reburn it. Normally, smoke isn’t completely consumed in the burning process, because some wood gases require temperatures as high as 1,200F to burn wood efficiently. A catalytic combustor lowers this required temperature to 600F, achieving a long, slow, controlled combustion that burns off the smoke that otherwise would leave the chimney as dirty, wasted fuel. The catalytic combustor needs minimal cleaning. If ash collects on the face of the com- bustor it can be cleaned with a soft brush. The internal “honeycomb” portion should never be cleaned with anything. It needs to be replaced after two to three years of normal use. Sluggish stove operation, creosote build-up and excessive smoke coming out of the chimney signal the need for a new combustor. Noncatalytic (recirculating) stoves use a heavily insulated firebox. This insulation keeps the heat in, creating a hot environment that encourages more complete combustion, with a secondary combustion chamber to burn off more gases and soot particles. “Noncats” don’t need as much attention as “cats,” primarily because they don’t have a combustor to maintain. Due to the new regulations, both types should provide comparable long-term performance.
What to look for in a stove with a catalytic combustor.
Materials and construction can affect how clean and efficiently your new stove will operate over the years ahead. Look for a stove whose body is made from cast iron or plate steel. The main body should be at least 1/4-inch thick. Because cast iron stoves have corners sealed with gaskets and cement, they may require a bit more maintenance. If the stove is catalytic, locate the bypass plate. It should be at least 5/16-inch thick. Test it by closing the plate on a dollar bill, which should grip it tightly. One of the most important things to look for is some sort of “flame impingement” mechanism designed to protect the combustor from direct flame, and thus from degrading prematurely. Some stoves have a flame shield in front of the catalytic combustor. Others use a series of chambers, or place the combustor to the rear of the stove.
What to look for in a noncatalytic stove.
Look for a stove whose body is at least 1/4-inch plate steel or cast iron, the two most commonly used materials. Inside, the most critical area is the baffle, in the roof of the main fire chamber. To resist warping, the baffle should be at least 5/16-inch plate steel, with v-shaped support beams. Note: the use of dry wood is much more important in a noncatalytic stove studies show that emissions can be three times as high when wet wood is used! Because the new “non-cats” are designed to pollute less at a lower burn rate, their fireboxes can be smaller than those in “cats.” This means they may require more frequent loading.
Shop around for the best stove.
Your stove will be part of your life for a long time, so it’s smart to get the best stove you can afford. Ask dealers about the points mentioned above, in relation to both their own products and the competition. Most important: talk to one or more chimney sweeps about the brands you’re interested in, and get recommendations from them. There’s no substitute for a third- party opinion based on practical experience.
Installing your Wood Stove.
Once you’ve chosen your new stove, your best bet is to have it installed professionally, for safety reasons. The record is not good on self- installations. Above all, don’t install your stove in confined spaces. Proper clearances, and professional installation, are vital elements in the safe, efficient operation of your stove. The installation guide included with your new wood stove will contain precise information about safety measures for that particular model. To insure a safe installation, call your local fire department and ask for an inspection.
Clearances are extremeley important.
When heat radiates into nearby combustible materials (the woodbox, magazine racks, furniture, draperies, wood paneling, flooring- even the studs behind plaster or sheetrock), it causes invisible changes in their composition, lowering the temperature at which they can burst into flames. Proper clearances can eliminate this danger The installation guide included with your new wood stove will contain precise information about the proper clearances for your appliance as well as instructions on how to connect the wood stove into an existing fireplace, and much more. To be sure, call your local fire department and ask for an inspection.
Ten Steps to maximum wood burning efficiency.
Wood smoke is caused by the incomplete combustion of wood. This can pollute the air indoors and outdoors as well as contribute to higher heating costs. Fortunately, the cure for cutting down on pollution and waste also cuts the costs by burning wood with safety and efficiency.
1. Burn seasoned wood. Up to 50% of the weight of green wood can be moisture, which has to be burned off before heat can be released into your house. Seasoned wood burns hotter and more efficiently, helps decrease the amount of creosote buildup in your stovepipe, and . you money.
2. Make your fires small and hot. This burns volatile gases more quickly, producing fewer safety hazards and air quality problems than a fire that is over-damped. Smaller, hotter fires mean more frequent loading and tending the stove…but the improved efficiency and air quality are worth the effort.
3. Install a stack thermometer on the stove flue. This will help you monitor the temperature of the gases as they leave the stove. Optimum range for most efficiency and least pollution: about 300 to 400 F.
4. Remove excess ashes. Too much can clog your stove’s air-intake vents and cut down on the amount of oxygen needed for woodburning.
5. Tighten up your house. Insulation, weather stripping, storm windows and caulking~ can all reduce the amount of wood required to heat your home, which in turn helps decrease the amount of air pollution.
6. Check your “smokestack.” Burn your stove at different rates, then go outside and check the emissions. The absence of smoke indicates that your stove is burning cleanly and effectively.
7. Inspect your stove. Once or twice a year, depending on how often it’s used, your entire stove and chimney should be inspected. Look for warping, check the baffle to make sure there are no gaps, check for creosote. Your dealer can make regular inspections, and so can a chimney sweep.
8. Choose the proper size stove. A properly sized wood stove will do its job efficiently even on the coldest days. One that’s too big needs to be damped down, which increases creosote production. The insulation in your home is a factor as well. To be sure you select the right-size stove, take along to your dealer the number of square feet to be heated, and the amount of insulation surrounding the area to be heated.
9. Buy the most efficient design you can afford. It’ll pay for itself in the long run. Research has made great strides in designing fireboxes, drafts, catalytic combustors and other devices that improve combustion and reduce smoke. Maybe it’s time to retire that old “smoker” and modernize.
10. Burn only the fuel your stove was, designed for. Don’t burn coal in a wood stove, for example, unless your stove was designed to handle both wood and coal. Trash shouldn’t be burned in your stove eitherbesides increasing the chance of starting a chimney fire, some plastics and other trash emit harmful gases, and can ruin your catalytic combustor. Driftwood, treated wood, artificial logs, or anything containing plastics, lead, zinc or sulfur will damage your catalytic combustor.
Call the Chimney Sweep!
There are two main reasons for keeping your chimney and stovepipe clean: to reduce the possibility of fire and to maintain the efficiency of your wood stove. You can do your part by operating your stove correctly, and by brushing or vacuuming the catalytic combustor gently. But for serious cleaning and preventive maintenance, you should develop a relationship with a good chimney sweep. This professional will make sure your chimney is in good repair, check the stove for leaks or cracks in the housing, and look over the catalytic combustor for signs of damage or deterioration.
The last word on wood
Different types of wood have different heating values. You should expect to pay more for a cord of mixed wood containing a lot of seasoned hickory, for example, than an equivalent measure with mostly aspen or hemlock. Generally speaking, you’ll get much more heat from hardwood than from softer, lighter wood. Most firewood you purchase will be green and have a fair amount of water in it. It takes at least six months of air drying for wood to be considered seasoned and ready for burning. When selecting wood, also take into consideration ease of splitting, ease of ignition and burning, how much smoke it produces and its “coaling” qualities. “Coaling” refers to the ability of a species of wood to form a long- lasting bed of hot coals when burned. Coaling qualities improve with higher density.
© 1992, CONEG Policy Research Center - Reprinted with permission.