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- Feb 1, 2015
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Creosote buildup is largely due to lower flue gas temperatures due to water content in the wood. While water is a combustion product, dry wood burns hot enough that the creosote doesn't condense in the chimney. A properly insulated chimney also helps to keep creosote accumulation down.
When I first moved in, our chimney was exterior to the house and made from concrete chimney block. Creosote would bui;ld up over the course of the heating season to the point where the chimney was completely blocked. About 30 years ago, I installed a 35' fully welded stainless liner in the old chimney running through the center of the house. Vermiculite was poured around the outside of the liner for insulation. Some creosote does build up over a heating season but it flakes off the liner and drops to the cleanout below. In thirty years, I have never had to clean the chimney.
When I installed our Big Jack wood furnace some twenty years ago, I took their advice and added a barometric damper. I fairly quickly disable it. Should the ever be a runaway chimney fire, the damper would open proving oxygen for the fire. I also modified the forced air intake by adding a solenoid controlled damper to it, shutting off combustion air when heat wasn't called for. There is a small amount of air flow owing to the motor cooling circuit but it fairly effectively shuts off air flow into the furnace during idle periods.
