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Thinking about Firewood

Posted: March 31, 2015

After a colder than normal winter in the Northeast, the last thing you want to think about is firewood. But now is the time to turn your thoughts to next winter and start caching your wood. Burning unseasoned, or worse green, wood is problematic because you lose heat, you create more smoke, and you increase unwanted fire risk as residues collect in venting systems.

Some pundits are suggesting that heating with wood is experiencing another surge in popularity. The last big turn to wood was in the 1970s following the oil embargo. Then, the focus was on woodstoves inside the house, where many found comfort in intense warmth. At the same time, many learned about the puffs of smoke, the never ending sweeping up of sawdust, bits of bark, and ashes after the inevitable cleaning. Today, you increasingly see outdoor heaters standing outside or with their short chimney poking up through a tin roof of the small shelter some erect over the stove to protect it and the wood pile. Other times you first notice the blue-gray smoke wafting across the yard and look around for the source.

Smoke is a concern with wood heating. Wood smoke is full of chemicals that threaten our health and the air we breathe. Smoke and wood are like soup and sandwich, they come together; however, with planning and forethought it is possible to reduce the amount of smoke. Without getting too technical, smoke contains four parts: particles such as ash, unburned volatiles, carbon compounds (think carbon dioxide), and water

After a colder than normal winter in the Northeast, the last thing you want to think about is firewood. You might still be wondering if there is enough to get through the last few weeks, but now is the time to turn your thoughts to next winter. It will be here before you know it and you want to have dry wood ready. Burning unseasoned, or worse green, wood is not a good idea because you lose heat (which means you need more wood to heat the house), you create more smoke, and you increase unwanted fire risk as residues collect in venting systems.

When firewood has high water content, full combustion does not happen until the moisture is driven off. When wood is wet, the fire smolders and the heavy blue smoke is full of water and chemicals. You can smell the difference; it is acrid and harsh. When dry wood burns in a woodstove with adequate air flow (not a dampered down, smoldering fire), the volatiles burn. On the other hand, when wood is wet, even with adequate air flow, the fire still tends to smolder as the water driven off by slow combustion cools the fire. In this case, there is no flame and lots of smoke. It takes heat to drive off that excess moisture and that heat is lost as the moisture vapor carries it up the chimney. The wetter the wood, the more difficult it is to burn.

The conventional wisdom is that firewood in our climate should be cut, split, and covered for at least nine months to a year before burning. By doing this the wood will have time to lose water due to evaporation and will approach equilibrium moisture content, which for Pennsylvania is around 16 to 20 percent. Achieving this desirable dryness takes time and work. Ideally, it would be great to have a two year supply of wood at the ready at the beginning of each heating season. At the least, you should be working on next year’s wood right now and have it stacked and ready to go by mid-fall.

Cut, split, and stacked is the admonition. Split wood to expose as much surface as possible and to reduce the cross-section so it loses water more quickly. Stacking takes space and is not a haphazard process. Ideally wood stacks should be under roof or at least covered, but in a way that moisture laden air can escape – covering with a tarp that traps water is not the best solution. To encourage drying elevate the stack on runners or pallets. This allows air to move up through the stack. Expose the stack to air and sun, which further accelerates drying. As the fall approaches, if you “smack” dried pieces together, you will hear the tonal difference. Dry wood nearly rings when ready.

Heating with wood provides great exercise, a sense of pride, a different level of comfort; however, it takes time and commitment. For your health’s sake, make sure you are burning dry wood. If you are splitting the wood right before it goes into the stove, or worst yet, burning it in the round all the time, you are likely wasting heat by sending water and volatiles up the chimney and creating more smoke than necessary. Burning dry wood saves money and reduces smoke. Cut your wood now. Follow the safety rules, and get ready for next winter. It comes around every year.

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of free publications, call 800 235 9473 (toll free), send an email to RNRext@psu.edu, or write to Forest Stewardship Program, Natural Resources Extension, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802. The Pennsylvania DCNR Bureau of Forestry and USDA Forest Service, in Partnership with Penn State’s Department of Ecosystem Science and Management, sponsor the Forest Stewardship Program in Pennsylvania.

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Contact Information

James Finley, Ph.D.
  • Professor Emeritus of Forest Resources
Email:
Phone: 814-863-0402