Heating with Wood Needs Care and
As people remember last winters high energy costs, many people
may use this fall as a good time to gather wood for heating the
home. Remember that although wood can be a good source of heat,
it should be used with caution and proper maintenance should be
done to avoid fires and chimney problems. Care should also be taken
to ensure that the use of wood is really more efficient and economical
for the home than the use of routine heat sources.
When considering the use of wood for heat, University of Illinois
Extension foresters offer the following information and advice:
All species of wood has the same Btu (British Thermal Units) per
pound of wood; roughly 8600 Btu per pound @ 15% moisture content.
As the moisture content goes up in the firewood, the heating value
goes down (less Btu's) because more energy (heat) is needed to drive
off the moisture in the wood before it will burn. This is why firewood
needs to be seasoned at least 6 to 9 months before it is burned.
Freshly cut wood is not very efficient for heating use.
The difference in the heating value of different species of trees
comes in the density (weight per unit of volume) of the wood species.
If comparing two pieces of wood that are of identical size (volume)
and moisture content and one is oak and one is cottonwood, the piece
of oak firewood will contain more Btu's (heat) in it than the cottonwood
because the density of oak is much greater than cottonwood. Oak
is a heavier wood than cottonwood, so oak will have more potential
energy than cottonwood if the same size piece or stack (volume)
of wood is compared.
Therefore, a cord of oak firewood would have 26.5 million Btu's
of energy and a cord of cottonwood would have 16.1 million Btu's
of energy, because a cord of oak weighs 3800 pounds and a cord of
cottonwood weighs 2300 pounds. A cord is a stack of wood that is
4 feet high by 8 feet wide and each of the pieces is 4 feet in length
or 4' x 8' x 4' = 128 cubic feet. The variety of wood and total
Btus should be considered when purchasing and pricing cords
For more detailed information, there are several university Extension
web sites across the country that offer good information on safely
selecting, cutting, drying, storing, evaluating and pricing wood
for firewood, including
Virginia Tech: http://www.ext.vt.edu/pubs/forestry/420-003/420-003.html;
North Carolina: http://www.ces.ncsu.edu/nreos/forest/woodland/won-14.html
October - November 2001: Preparing
Plants for Winter | Heating with Wood Needs
Care and Consideration | Amaryllis for
Winter Beauty | Understanding Fall Color