Wood Stove Size Vs. Chimney Size

Stovepipe and Flue

• It's important to choose a wood stove with an outlet that's appropriate for the size of the chimney's flue, according to the U.S. Department of Energy. The flue is the opening in the chimney that allows smoke to escape. The stove outlet, or stovepipe, connects the stove to the chimney. The DOE indicates creosote accumulates, and the stove's efficiency drops, if the chimney flue is too big for the stovepipe. Creosote is a flammable material that builds up when wood doesn't burn completely. A large amount of creosote can ignite inside the stovepipe or chimney, starting a fire that can spread throughout your home.

Sizing

• A reputable stove installer can help you choose a wood stove with a stovepipe that properly fits your chimney flue. The flue size generally needs to be 25 percent bigger than the size of the stovepipe, according to the University of Missouri Extension Service. Therefore, a stovepipe with a 6-inch diameter needs a flue that measures about 8 inches. The flue needs to be larger to allow sufficient space for smoke to escape so that it doesn't circulate back into your home.

Chimneys

• An existing chimney built for a coal, gas or oil furnace likely can't be used for a wood stove without modifications, according to the Cornell Cooperative Extension Service. The organization indicates that most pre-existing chimneys and flues are too big for wood stoves. Furthermore, your local building codes may prohibit connecting a wood stove to a flue if it's already in use. Connecting your stove to a separate flue may increase the stove's efficiency.

Flue Shape

• The shape of a flue may affect how well smoke passes through it, even when your flue and stovepipe sizes are correctly matched. The University of Missouri Extension Service indicates that round flues are more efficient, because smoke moves out of a wood stove in a swirling motion that's unobstructed by a circular flue. Square and rectangular flues can be less efficient, because their shape doesn’t support the natural flow of smoke.