How Seal a Wood Burning Flue

Options

• Both commercially manufactured and homemade flue seals work equally well to prevent air leaks in wood-burning heat sources. So deciding which flue seal to use is mostly a matter of personal preference. Most modern fireplace and wood stove manufacturers produce flue seals that are designed specifically for their current models, and so it is best to opt for a commercially made flue seal if at all possible to prevent voiding the stove or fireplace's warranty. Creating a homemade seal that will work on a variety of flues, however, is simple and requires only a few materials.

Installation

• Installing a commercially fabricated flue seal according to its manufacturer's directions provides the best results and maintains the stove or fireplace's warranty. Creating a homemade flue seal begins with measuring the inside of the flue opening just below the damper and adding 1/2 inch to the measurement. Cut a portion of 4-inch thick foam rubber so it matches the measurement. Covering the foam rubber in heavy plastic protects it from degradation, and duct tape will secure the plastic. The result is a flue seal. A long, brightly colored portion of string or plastic attached to the side of the flue seal serves as a visual reminder to remove the seal before starting a fire. Press the seal into the flue until it rests against the damper with the brightly colored string hanging down where it is plainly visible.

Maintenance

• Because the flue seal must be removed before using the wood-burning unit, it is simple to catch possible issues with its integrity before they become serious. Inspect the flue seal each time you remove it, looking for cracks in the materials and signs of dampness. Homemade flue seals require yearly resealing to keep moisture out of the foam rubber center because excess moisture will eventually damage its flexibility, which will cause it to produce an insufficient barrier against air leakages. Replace the flue seal with a new one if significant damage appears.

Cautions

• Installing a flue seal is safe if done correctly, but it is important to allow the flue to cool entirely before putting the seal in place. That course of action will prevent injury to the person installing the flue seal and prevent damage to the seal. As a rule of thumb, it is best to wait at least four hours before putting the flue seal in place. Also, it is vitally important to remove the flue seal before lighting a fire in the wood-burning heat source because the seal prevents smoke from entering the chimney, posing a health hazard and negatively affecting your home's interior.