How Do You Prevent a Chimney Downdraft?


Quick Answer

Removing obstructions from within or around a chimney or raising its height can help prevent downdrafts. Chimneys that suffer from internal obstructions such as soot deposits or external obstructions such as overhanging branches may be unable to produce a good updraft. The installation of a wind-resistant chimney cap can also prevent downdrafts from occurring.

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Full Answer

Chimney operation depends on hot air being able to rise. The movement of hot gases rising from the fire creates currents that draw air in from the surrounding environment, which then feeds the fire. Chimneys that suffer from downdrafts can suffer numerous problems including the inability to light or maintain a fire, excess smoke, and poor heat output. Removing obstructions that may be impeding airflow within the chimney can help to ensure proper airflow and operation.

Hot air rising from a fire creates zones of different air pressure throughout the interior environment. Fireplaces located within areas of low pressure commonly suffer from a permanent downdraft. A simple way to prevent this from happening is to open a window in the room containing the fireplace to equalize the air pressure. Installing a metal or masonry chimney cap over the top opening of the chimney can also prevent downdrafts by altering the air currents and increasing the height of the chimney.

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