4 Causes of Creosote Buildup

Have you noticed smoke flooding into your home when burning a fire in your fireplace or wood stove? Or maybe you’ve noticed that bits of debris have fallen from the flue into your fireplace or stove? These are signs you have a creosote buildup on the inside of your chimney flue.

Creosote is a black or brown residue that sticks to the inner walls of your chimney or stove pipes. In texture, it can appear crusty or flaky, drippy and sticky like tar, or shiny and hardened to the surface. But whatever its appearance, creosote is highly combustible. And it creates a serious fire risk.

Certain conditions that can cause creosote buildup include:

1. Cool flue temperatures. When the temperature inside your flue is cooler than normal, smoke will condense, causing creosote form on the inner walls at an accelerated rate. Metal chimneys are very susceptible to creosote buildup. Their light sheet metal construction helps to keep the interior flue temperature abnormally cool. Also the location of the chimney can affect the interior temperature. A chimney on an exterior wall can be affected by outside cooler temperatures while a chimney located on an interior wall is usually warmer.

2. An oversized flue. If your home has an older fireplace insert or a hearth-mounted stove that’s vented into a masonry chimney, chances are, your flue is too large to support the fireplace insert or stove. So the smoke from a fire can hang around in the chimney for a longer time (called residence time), leading to creosote buildup.

3. Restricted air flow. Not only does an oversized flue confine air supply in a chimney, but closing the glass doors on a fireplace or stove too tightly, or failing to open the chimney’s dampers wide enough can hamper the amount of air flow in your chimney. In these conditions, the restricted air flow prevents the smoke from leaving and increases its residence time. Again, enabling creosote buildup.

4. Use of unseasoned firewood. Firewood that’s unseasoned or dried insufficiently contains water. When unseasoned firewood is burned, it creates less heat because most of the fire’s energy is used to burn away the moisture. Since the fire is cooler, the smoke condenses quickly, forming creosote on the flue’s surface.

While you could try to remove any creosote yourself, it can be a messy, dirty job. And if the creosote is hardened to your flue’s surface, it’s best to have a professional clean it. So, hire a professional chimney sweep, like T.J.’s Chimney Service, to inspect and clean your flue in the first place. You’ll save yourself time and guarantee that your flue is thoroughly cleaned. Call T.J.’s Chimney Service at 317-455-5310 to schedule your chimney inspection and cleaning today.