Do You Waste Money by Heating With Wood? (News Release)

Using a wood heater can reduce your heating costs, but many Tennesseans spend more by heating with wood than if they relied solely on their primary heating systems. Savings from using a woodburning heating system depend on installation costs of the wood heating system and the fuel costs and efficiencies of both the primary and wood heating systems. This article focuses only on the fuel costs.

The type wood and its moisture content are extremely important factors determining heating value. Dense woods, such as hickory, red maple and oak, have the highest heating values. Seasoned firewood, air dried for at least six months while protected from precipitation, burns easily and efficiently. Freshly cut firewood contains so much moisture that half the heat from burning the wood is required to dry it so it can burn.

A fire in the fireplace is relaxing, but you will be warm on one side only. Fireplaces deliver ten percent or less of the fire's heat to the room and will increase your heating bill in two ways. First, firewood costs more than the value of the delivered heat. Seasoned oak firewood must cost less than 20 dollars per cord (a cord is a stack 4 feet wide by 4 feet high by 8 feet long) to provide heat from a fireplace at a cost comparable to a heat pump. Fireplaces also require a large volume o air which. The incoming air cools the rest of the house, causing the primary heater to operate more than if you had no fire.

Airtight stoves operate at about 50 percent efficiency, and wood furnaces at about 70 percent efficiency. These can decrease your energy costs, but the firewood must cost less than about 100 dollars per cord for the airtight stove, and less than 130 dollars per cord for the furnace, to provide heat at costs comparable a heat pump. Green wood must cost less than one-half the figures shown to be cost effective.

Get the most from your wood heater by using it to complement your primary heating system. Learn the strengths and weaknesses of each system, and operate each for its maximum advantage.

Woodburning heaters perform best when delivering a moderate to high heat output. Maintain a moderate fire, with the temperature of the stovepipe between 300 and 450° Fahrenheit about 18 inches from the stove. This can be achieved by adding small amounts of wood periodically and regulating the air supply. Cooler operating temperatures allow excessive creosote buildup, but 600° Fahrenheit can ignite creosote and cause a chimney fire. A smoldering fire does not burn wood efficiently, nd creosote and other products of incomplete combustion clog the stovepipe and chimney. The interior of a cool stove is also coated by creosote, insulating the stove and reducing the heat output.

Conventional heating systems operate at constant efficiency throughout the winter, with the exception of heat pumps. Heat pumps are very efficient when the outside temperature is above freezing, and efficiency increases as the outside temperature rises. However, heat pumps must work harder at subfreezing temperatures because there is less heat available to extract from outside air. In extremely cold weather, heat pump systems rely on costly resistance heat.

The amount of heat your system must deliver is directly proportional to the difference between the indoor and outdoor temperatures. With the thermostat set on 68 degrees, your house requires twice as much heat when the outside temperature is 28° as when the temperature is 48°.

Each 2° you raise the thermostat setting above 68° will increase your heating requirement by 10 percent when the temperature is 48° outside. If the outdoor temperature is 28°, each 2° thermostat setting increase will increase your heating requirement by 5 percent. Combined with the increased heat requirements of colder weather, increased thermostat settings can become very costly.

What does all this mean? When the weather is mild, consider operating only the primary heating system because you need little heat. Wood heaters arc difficult to regulate for comfort in mild weather and the smoldering fire produces excessive creosote. Use the wood heater in colder weather, maintaining a moderate heat output for efficient combustion. However, use a fireplace only in mild weather so it will not cool the rest of the house.