University of Illinois Extension

Firewood, BTUs and Bugs

There's nothing like stepping outside and smelling the smoke coming from the fireplace during the cold winter months.

Richard Hentschel

"The expression of 'you get out of it what you put into it' is really 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 Hentschel. "Typically the harder the wood, the more heat (BTUs) you are going to get."

Some of the better woods are oak, hard maple, ash and 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.

"Those harder woods will be easier to burn and smoke less than softer woods," he said. "Another benefit of burning the better woods is you will not have the amount of sparks coming from the firewood that you would get if burning the softer woods. The better woods are also heavier per piece, being more dense, 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. Homes that are well insulated and 'tight' will need to crack open a nearby window or be able to supply the combustion air to the fire box."

Salt Damage on Yews Firewood generally should be seasoned to dry down for at least nine months and should have a moisture content of about 20 percent when we 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, little heat and can add creosote to your chimney flue and pollutes the air.

Homeowners should only bring in firewood that will be burnt over a period of a few hours. "Insects that use the firewood as part of their life cycle or just 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 those adult insects that are there looking for a place to overwinter.

"There are many boring insects that use or feed on dead trees that can invade your firewood while it is seasoning. You could also get carpenter ants, especially if the firewood has not been moved or used in a long time or seasoned properly. There are a great 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 you buy and while the definition 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. "