Wood Burning Fireplaces and Stoves

September 7, 2008 by  
Filed under 02: Wood Burning

While wood-burning fireplaces may be wonderful for setting a romantic mood, they are relatively inefficient devices for heating the home. On the average, an operating open-masonry fireplace can have efficiencies ranging up to 15 percent, depending upon its type and operation. However, the efficiency story gets worse — if there is no fire and the damper is left open, a fireplace can actually have a “negative efficiency” as warm air from the house escapes through the chimney.

Fortunately, there are ways to improve wood-burning fireplace efficiency:

Dampers

When a fireplace is not is use, the damper should be in the closed position. Since hot air rises, it naturally wants to escape through the chimney. Closing the damper seals off this avenue of escape.

Glass or Metal Doors or Heat Shields

Placed in front of the fireplace, these sorts of devices will limit the amount of warm room air that escapes the house when the fireplace is not is use.

Doors work particularly well when a fire is burning down for the night, but the damper has to remain open to allow the smoke to vent.

While the fireplace is in operation, glass doors should remain open, since most of the warmth produced by a fireplace is in the form of radiant heat. If closed, the glass will deflect radiant heat back into the fireplace and reduce the heat output to the room. In California, masonry or factory-built fireplaces require closeable metal or glass doors covering the entire opening of the firebox.

New Fireplace Designs

Circulating fireplaces have heat circulation ducts built into the masonry fireplace. These pull air from the room, circulate it around a metal firebox and send it back, warmed, into the room.

Some of these units have built-in fans to increase the flow of air and heat. Made of metal, circulating fireplaces warm quickly and cool rapidly once the fire is extinguished.

Fireplace Inserts

An insert is basically a metal wood stove that slides neatly into the fireplace cavity. They are relatively easy to install, and can improve a fireplace’s efficiency. Before adding one, however, make sure to have your fireplace and chimney inspected and cleaned.

As a matter of fact, that’s a valuable tip in any case — for the most energy efficiency from your fireplace and to insure your family’s safety, have your fireplace and chimney cleaned and inspected at least once a year.

Wood Stoves

You can also increase your fireplace’s efficiency — if not its beauty — by installing a wood stove in front of it. The existing fireplace chimney becomes the exhaust for the stove. Inspect, clean and repair your chimney first, and check with your local building department or air pollution control to see if either a wood stove or insert is allowed.

Wood stoves can be added without a fireplace, of course. There are many types of wood stoves on the market today; if you’re to buy one, choosing from the many styles, models and options can be a difficult task. Remember that stoves can be expensive to buy initially and costly to operate if you’re going to buy wood. And they can also be dangerous — make sure you educate the occupants of your home about the potential safety hazards.

Before you buy, make sure a wood stove meets local air quality regulations. As a rule of thumb, the more efficient the stove, the less pollution it produces. Check with your local air pollution control to see if there are regulations covering how efficient your stove must be.

According to the Environmental Protection Agency in the U.S., the use of wood for residential heating contributes up to 50 percent of the polynuclear organic air pollutants, some of which may be carcinogenic. During winter months, in areas where wood is the principal heating fuel, Wood stoves produce as much as 80 percent of these type pollutants.

Once you’ve bought and installed a wood stove, notify your local building department to conduct a final inspection to ensure that all safety requirements are met before you use the stove.