Purdue News

December 2, 2005

Purdue expert: Firewood has pros and cons for home heating

WEST LAFAYETTE, Ind. - The high home heating costs predicted for this winter have many people looking for supplemental and alternative heating sources, like wood-burning stoves, for their homes.

"Wood, when it's readily available, is a pretty inexpensive source of home fuel," said Dan Cassens, a professor of forestry and natural resources at Purdue University.

However, burning wood does have some drawbacks, like efficiency, he said. It takes approximately 4,400 pounds of high-quality firewood to equal 21 therms of gas, or about 4,700 kilowatt hours.

"It's difficult to evaluate the efficiency of wood as a fuel," he said. "The fuel value of wood depends on the species weight and moisture content and is extremely variable. For the same volume, some types of wood may contain twice as much heat as others."

High-quality, seasoned hardwoods, such as hard maple, oak, ash and hickory, produce more heat than lighter woods like buckeye, cottonwood and willow.

"It's not a good idea to burn pine," Cassens said. "The pitch in green pine causes excessive creosote buildup in chimneys." Pitch is a sticky, saplike substance.

The type of heating system used also affects the amount of heat produced.

"Typical masonry fireplaces only recover about 10 percent of available heat, while some better designed wood stoves have 50 to 75 percent efficiency," Cassens said.

He said it's also difficult to get heat from a wood-burning stove to travel from room to room.

All of these reasons mean that wood makes a good supplemental heating source, but it can be just as expensive as gas or electric as a primary heat source. There also are other concerns about burning wood.

"Unfortunately, house fires can occur if stoves are improperly installed or carelessly maintained and operated," Cassens said. "Always consult your local building code officials before installing a wood-burning stove. Some states also recommend that you consult the fire marshal and your insurance agent before installing the stove."

It's also important to keep children away from the fireplace or stove and to monitor the stovepipe temperature.

"Smoldering fires or green wood can cause creosote to build up in the stovepipe and catch on fire," Cassens said.

A thermometer on the stovepipe will indicate when the fire is too cool, which creates a possibility for creosote formation, or too hot, which creates a fire hazard.

Recently foresters and entomologists also have been cautioning people about transporting firewood.

"Firewood, especially firewood with the bark still attached, is a good way for invasive insects to travel throughout the state," said Jodie Ellis the exotic insects education coordinator at Purdue. "We recommend that people buy their firewood close to where they'll be burning it. It's also a good idea to burn all your firewood, rather than keeping it for extended periods of time."

Writer: Kay Hagen, (765) 494-6682, kjh@purdue.edu

Sources: Dan Cassens, (765) 494-3644, dcassens@purdue.edu

Jodie Ellis, (765) 494-0822, ellisj@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
Agriculture News Page


Related Web sites:
Wood for Home Heating

Residential Wood Stove Installation


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