With Green Firewood, Savings Go Up in Smoke

With Green Firewood, Savings Go Up in Smoke


By Jeanne Huber (reprinted courtesy of the Washington Post)

Q. With heating bills so high, I plan to use our fireplace more than we have in past winters. But how do I know if the firewood I buy is dry?

A. Heating with wood can be a viable alternative to burning oil or natural gas, but if you're just gearing up for it now, you're right to be concerned about buying dry wood. If lots of people are contemplating having more fires this season, there might be a shortage of the well-aged logs that will actually save you money.

If you were to burn green wood, you wouldn't get much heat because a lot of the energy stored in the fibers would just go into evaporating the moisture within the wood. The amount of water can be considerable -- equal to half or more of the weight of the wood. Plus, the cool-burning fires produced by green wood create a lot of smoke, which results in air pollution and leaves thick deposits of creosote building up in your chimney. That, in turn, can lead to a chimney fire, which can wreck the chimney or even start a house fire.

The firewood you use now should have been cut early last spring, or even earlier. So you might start by asking when the wood was cut. If the wood was split then and stacked to dry in the sun and wind, the moisture content now should be below 20 percent. Depending on the weather, it may drop down to 12 percent or even lower. If you have access to a moisture meter, you can check the level precisely. Meters typically start around $130, so it's probably not worth buying one just to check firewood. However, if you're buying wood from someone who's in the business of providing it, you might ask whether he has a meter; if so, ask for a test you can witness. Or if you have friends who do a lot of woodworking, ask to borrow their equipment.

There are also some less precise ways of evaluating firewood:

Touch the wood. Freshly cut pieces are noticeably damp, especially on the ends.

Look at the bark. If it's still firmly stuck to the wood, the firewood was cut recently. If the wood lacks bark or if you can pull it off with your hands, that's a good sign.

Check the ends. If the wood is newly cut, you will see a series of circular rings, showing how the tree formed wood in annual layers. If you also see cracks that run perpendicular to the rings, you know that the wood is dry or at least is headed that way. Wood fibers shrink as their moisture evaporates, but the shrinkage doesn't occur evenly. So some of the fibers inevitably pull away from each other, forming the cracks.

Bang a couple of pieces against each other. If you hear a hollow crack, the wood is dry. If the wood makes a dull sound, it's still wet -- or rotten.

Like green wood, rotten wood isn't worth burning. Even if it's dry when you buy it, you won't get much heat because the fungi that cause wood rot will have already removed most of the energy-rich ingredients. The heat value of firewood is mostly related to its weight, provided the weight isn't water, and rotted wood is very lightweight.

The visual and audible clues about whether wood is dry and still worth burning are obviously quite subjective. So it's probably no surprise that consumers often complain that they were sold wood that wasn't as good as they were told it was. When you purchase wood in the fall, always inspect it before you pay. In the spring, you don't have to be as careful, especially if you are dealing with a supplier who cultivates long-term business relationship with you.

The other big source of consumer complaints about firewood centers on the quantity of wood purchased. Most people know that wood is often sold by the cord, but they're often unclear what that means. A cord of wood consists of pieces stacked as compactly as possible into a pile 4 feet high, 8 feet long and 4 feet deep. A "face cord" is a pile just as high and long but only as deep as the length of the pieces. If pieces are 24 inches long, a face cord equals half a standard cord. If pieces are 16 inches long, a face cord is just one-third of a standard cord.

It's difficult to pinpoint the prices at which firewood becomes a better bargain than heating oil or natural gas because the efficiency of furnaces and stoves varies considerably. However, you can assume that burning wood in a fireplace won't save money, says James E. Johnson, an associate dean in the Department of Forestry at Virginia Tech's College of Natural Resources. "A fireplace is nice for a little bit of mood," he says. "But it is not a heating device unless it's an emergency when the power is out." Except in Rumford fireplaces, which can be efficient at heating a space, burning a fire can actually suck heat out of your home because of the quantity of air that goes up the chimney. Fireplace inserts, free-standing wood stoves and wood-burning furnaces are far more efficient.

© 2005 The Washington Post Company
This article is the third of a three part series. For the other two go to the community web site at www.lakebarcroft.org/association/newsletters-reports/firewood-1 and www.lakebarcroft.org/association/newsletters-reports/firewood-2