Wood for Home Heating Needs Care and Consideration - U of I Extension

News Release

Wood for Home Heating Needs Care and Consideration

This article was originally published on December 1, 2018 and expired on February 17, 2019. It is provided here for archival purposes and may contain dated information.

"Each fall and winter there are questions about using wood as a source for home heating, especially when trying to save on energy consumption", 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.

When considering the use of wood for heat, University of Illinois Extension foresters offer the following information and advice. All species of wood have the same Btu (British Thermal Units) per pound of wood; roughly 8600 Btu per pound at 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 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 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.

Heating with Wood

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 Btu's should be considered when purchasing and pricing cords of wood for heating purposes.

The University of Illinois also has an excellent website which details information on trees, wood and woodland management, as well as links to other wood web sites, at http://web.extension.uiuc.edu/forestry/timber_harvest/firewood.html.

Please remember that bringing firewood from outside of your county is not recommended because of the threat of transporting emerald ash borer or other pests. Check this web site for more information on emerald ash borer: http://www.agr.state.il.us/eab

For more 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 the University of Nebraska's "Heating With Wood: Producing, Harvesting and Processing Firewood", publication G1554 located at http://ianrwww.unl.edu/pubs/forestry/g881.htm and then do a search for heating with wood.

Source: John Church, Extension Educator, Natural Resources Management, churchj@illinois.edu

Pull date: February 17, 2019