Weathering Woodstove Woes
By Lisa Munniksma | Oct 6, 2020
Photo by Adobe Stock/Nathaniel Asaro
Woodstoves are among the least expensive forms of home heating, enabling self-sufficiency and comfort that other heat sources don’t provide. They’re not without their share of work, though, both to keep you warm and to keep the stove maintained.
Even the most seasoned woodstove users will run into operation issues now and then; this article can be a refresher course for those folks. For green woodstove users, this summary of four common problems will help you better operate, maintain, and ultimately enjoy your woodstove.
Smoke Without Flame
Wood smoldering in a stove is most often not an issue with the woodstove, but rather an issue with the wood, according to Daniel Ciolkosz, assistant professor and research associate for Penn State Extension. Wood that smolders rather than burns likely hasn’t been properly seasoned.
Wood should be allowed to dry for at least one year after it’s been cut, preferably two years, particularly for hardwoods. Less than 20 percent moisture by weight is ideal for burning. Fresh-cut wood typically has 45 to 50 percent moisture.
“Moisture makes it harder for wood to heat up and properly burn,” Ciolkosz says. You can test moisture content with a moisture meter or by feel. “Once you’ve been doing this awhile, you’ll get a good sense of the wood’s moisture content by knowing the kind of wood it is and how it behaves when fully dry: Oak will still be very heavy compared to pine, but will have checks or cracks in the end grain, and there’s a crisp sound when you knock two pieces together — like musical woodblocks,” says Guillermo Metz, the energy team leader for Cornell Cooperative Extension.
Cutting and stocking up on wood requires planning as well as covered storage space. For truly seasoned wood, Metz suggests cutting and stacking wood for burning two years later. Alternatively, if you trade for or purchase wood as you need it, ask about the source and age of the wood to determine whether it’s fully seasoned.
Another low-burning wood issue can be the size of the pieces. “If your wood is properly seasoned, but you start with wood that’s too big, it won’t be able to reach temperatures to actually burn well. You need to start with kindling — not just small pieces, but what many would consider very small pieces of wood, not much bigger around than your thumb. Stack a few of those with some crumpled-up newspaper, and let that catch before adding progressively larger pieces,” Metz says.
A third possible cause of smoldering wood is an issue with the stove: If the air inlet is blocked with ash, the stove won’t be able to draw enough air to fire the wood. “That will obstruct the airflow and cause problems with burning,” Ciolkosz says. “No one likes to shovel out ash, but it’s important to keep up with it.”
Photo by Adobe Stock/GuruXOX
Fast and Furious
Different types of wood burn at different rates. “Pine and other softwoods will burn much quicker than hardwoods, such as oak or ash,” Metz says. Pay attention to how each type burns in your stove so you can control the stove’s heat output by adding wood based on your heat needs.
“The fire should always be burning hot. It’s important to use a woodstove thermometer to have a good idea of the temperature and to keep the fire in the optimal burning zone. Too cold, and the emissions will be higher (more smoke) and pose an increased risk of creosote buildup, which can cause a chimney fire; too hot, and you risk damaging the woodstove,” Metz says. The optimal burning zone will be marked on the thermometer, and is generally between 250 and 600 degrees Fahrenheit.
If you believe the wood is burning too fast, Ciolkosz says, “Resist the urge to think the air damper is a control switch. If you dampen down the airflow to reduce the amount of heat being produced, you’ll also reduce the ability of the wood to burn completely.” Dampening down the stove will send the smoke from the wood up and out of the chimney, rather than allowing volatile compounds to fully combust in the stove. It’s not the burning of the wood itself that produces the most heat from a woodstove. As the heat builds from the burning wood, the escaping gases begin to burn, and eventually, the log charcoal burns and emits most of the fire’s heat.
Chimneys should only smoke for about 10 minutes after you light a fire. Photo by Adobe Stock/MSCornelius
Smoking Like a Chimney
Metz says, “Smoke should only be going up the chimney flue when the fire is first lit, for about 10 minutes, and then no smoke should be visible if the fire is burning correctly.”
Smoke leaking through the joints in the stovepipe has several possible causes. The first is that the stovepipe isn’t fitted tightly enough or is otherwise incorrectly installed, so check the joints thoroughly. “The pieces of pipe aren’t typically sealed with caulk, so air can get in, but the smoke should be rising, not coming into the room. Get professional guidance about whether to add caulk, and make sure you’re using the correct, high-temperature-rated caulk, if you do,” Metz says.
The second potential reason for smoke leaking from the stovepipe is that the air pressure in your house is lower than the air pressure outside, causing a vacuum effect. This might be the result of exhaust fans running in an airtight house. It also could be related to the placement of the woodstove in your home; well-sealed basements may have negative air pressure. The remedy here is to let in outside air, whether that’s by cracking a window for a quick fix, or adding ventilation to your home’s structure for a more long-term solution to the pressure problem.
The third possible cause is wind blowing air from outdoors into the stovepipe, forcing air — and smoke — through the joints. In this case, Ciolkosz encourages installation of a better chimney cap.
And finally, “You can also occasionally get a downdraft in certain conditions, such as cold, still air outside not letting the warmer smoke rise up and out,” Metz says. “One way to help prevent this is to light a piece of rolled-up newspaper and hold it up as high in the burn box as you can, and just let it burn out there. This will help get the draft going by slightly warming the top of the burn box and the stovepipe. Do this after you’ve built up the wood in the stove, and then drop the newspaper on top of the wood pile to start the fire. Once the draft is established, it’s rare to get a downdraft during that burn. Again, keeping the fire burning hot will help maintain a good draft.”
Photo by Adobe Stock/Hosana
Being Smoked Out
You may notice smoke pouring into the room when you open the woodstove door to tend the fire. This problem is typically related to a downdraft, and can often be solved with the same tips listed previously for correcting smoke leaking through the stovepipe joints. “Always open the doors slowly to prevent backdrafts into the room,” Metz says. “Because there’s more oxygen in the room than in the firebox, the fire — usually just smoke — can jump into the room if you’re not careful.”
Along these lines, Metz says he too often hears of folks operating their woodstoves with the doors open. “You should only open the doors to put wood in and start the fire, or to add more wood. Always keep them closed the rest of the time. Keeping the doors open means there’s excess smoke and particulate matter going into the room rather than up the stovepipe. This is harmful, and the fire isn’t burning as well as it could,” he says.
Start fires with plenty of very small kindling. Photo by Adobe Stock/Lolostock
When to Call In the Experts
We all want to perform maintenance and troubleshooting ourselves, and the simple design of woodstoves allows us to do that — until it doesn’t. “Anytime you’re not 100 percent confident that what you’re going to do is safe, you need to call in a professional,” Ciolkosz says.
New woodstove owners might call a professional for help with regular maintenance and to learn from them. “Chimney sweeps are trained in all aspects of woodstove maintenance and safety and can spot issues that an untrained individual can’t. So, I always recommend hiring a chimney sweep for at least the first few years of woodstove ownership,” Metz says.
“Woodstoves are dependent on the operator — the emissions and efficiency of your woodstove are almost entirely a product of how you operate it,” Metz says. “It’s really important to keep your woodstove well-maintained, operate it properly, and burn only clean, dry wood (and a little newspaper to get the fire started — no other kind of paper).”
When you know how to solve these common issues and operate your woodstove efficiently, you’ll be able to enjoy the reward of using a woodstove for home heating.
Lisa Munniksma is a farmer, editor, and freelance writer. She lives in Kentucky.
All issues covered in this article, as well as a host of others, are preventable with user knowledge and equipment maintenance. Energy specialist Guillermo Metz suggests you regularly address the following maintenance tasks for woodstove safety and efficiency.
Clean your stovepipe and chimney each year. “You can purchase the stovepipe cleaner and do it yourself, but first have a professional show you how. If your stovepipe and chimney are consistently clean, you may be able to put off this task to once every two years.”
Check your door gaskets each year, and replace as needed. “A simple test is to hold a dollar bill in the door and close the door. If you can pull the bill out easily, the door is too loose; you should be able to pull out the bill, but with some difficulty. If it’s not the gasket, the door itself may be loose.” Conduct the same test with the ash bin door. Your owner’s manual will explain how to adjust the tightness of the doors.
Examine your stovepipe. “Are there rust spots or gaps between pieces? You can try addressing the latter by adding a few sheet metal screws to hold the pieces together better; the former may require replacement of the piece, and that you figure out why your stovepipe is getting wet in the first place.”
Check the fire bricks in the burn box regularly, and replace any that are cracked.
Search for “wood stove” (two words) to learn about effective, economic uses of your woodstove, as well as wood sources.
Learn about firewood storage, health and emissions, woodstove safety and maintenance, and best burn practices.
Learn how to burn wood cleanly for greater safety and efficiency, and less environmental impact.
Learn about new technology and the next generation of woodstoves.
Your woodstove manual.
Reading an operator’s manual is often the butt of jokes, but the manual will explain how the manufacturer intended your stove to be operated and maintained.
Ensure a good burn with a solar wood-drying kiln.
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