Firewood, BTUs and bugs
November 18, 2010
  • /Crop Sciences
The expression 'you get out of it what you put into it' is true when it comes to how much heat you get from burning your firewood, as well as how well it burns and how much smoke it produces, said a University of Illinois Extension horticulture specialist.

"Typically, the harder the wood, the more heat (BTUs) you get,"said Richard Hentschel.

Some of the better woods for burning are oak, hard maple, ash and the nut trees like hickory and pecan. On the lower end of heat output are the softer woods like soft maple, linden (basswood), willow and cottonwood.

"Harder woods burn more easily and create less smoke than softer woods," he said. "Another benefit of burning harder woods is you will have fewer sparks. The better woods are also heavier per piece, being denser. That's another clue you can use.

"Your fireplace, just like your furnace and gas clothes dryer, will need a source of outside air to burn properly. In homes that are well insulated and tight, you will need to crack open a nearby window or be able to supply the combustion air to the firebox." Firewood generally should be seasoned to dry down for at least nine months and should have a moisture content of about 20 percent when you are buying a face cord, longer if you are buying an actual full cord (4'x4"x8').

Burning high-moisture wood generates a lot of smoke and little heat, can add creosote to your chimney flue, and pollutes the air.

Homeowners should only bring in firewood that will be burned over a few hours.

"Insects that use the firewood as part of their life cycle or overwinter in the bark crevices have time to warm up and move out of the firewood if stored longer indoors," Hentschel said. "This is especially true of adult insects that are looking for a place to overwinter.

"There are many boring insects that use or feed on dead trees and invade your firewood while it is seasoning. You might find carpenter ants, especially if the firewood has not been moved or used in a long time or seasoned properly. There are many insects that seek winter shelter from the cold in the crevices of tree bark. None of these insects will typically pose a problem in your home and are just a nuisance until they die."

When storing your firewood, keep it away from the home, off the ground and in an area where there is good air circulation to aid in the seasoning process.

"Homeowners find that the cost of firewood will vary greatly, depending on the tree species, and while the definition of a full cord of wood is quite clear, the depth of a face cord will vary, as will the price," he explained. "A face cord that has 16-inch-long pieces is also referred to as a rick, stove cord or fireplace cord. There also may be a delivery charge to stack your firewood compared to just unloading it on the driveway."