What to know about using wood for home heating
"Each fall and winter there are questions about using wood as a source for home heating, especially when fuel prices are potentially going to be high", says John Church, University of Illinois Extension Educator, Natural Resources, Rockford. Before using wood as a source of heat, first consider necessary safety precautions and proper equipment maintenance to avoid fires and chimney problems. Secondly, 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 fuel sources.
The Illinois Forestry Web site on the University of Illinois Extension home page at http://web.extension.uiuc.edu/forestry/timber harvest/firewood.html contains excellent information regarding harvesting, buying and burning firewood for heat.
Forestry economists estimate that approximately two million cords of firewood are harvested annually from Illinois woodlands. Almost 43 percent of all annual wood removals are used as firewood and nearly 75 percent of all firewood is cut from dead or downed trees.
When considering the use of wood for heat, remember that all species of wood have the same BTU (British Thermal Units) per pound of wood; roughly 8600 BTU per pound at 15 percent 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 dry off the moisture in the wood before it will burn. This is why firewood needs to be seasoned at least six to nine months before it is burned. Fleshly cut wood is not very efficient for heating use.
The difference in the heating value of different species of trees is due to the density (weight per unit of volume) of the wood species. If comparing two pieces of wood that are of identical size (volume) and in 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.
The variety of wood and total BTU's should be considered when purchasing and pricing cords of wood for heating purposes.
For more detailed information, the forestry website also lists ten additional firewood related sites from across the country that offer good information on safely selecting, cutting, drying, storing, evaluating and pricing wood for firewood. Other forestry information is also on the Web site.