What Causes a Chimney Downdraft?

powers-3-2016A chimney is designed to pull air up and away from the home. However, some homeowners have experienced a chimney downdraft where air and smoke is drawn into the home. This can have dangerous implications. Other home components like the furnace and water heater are also connected to the chimney. This means if air is being drawn in instead of out, it can also draw in harmful gasses.

Common Culprits of a Downdraft

  • Soot and creosote build-up can cause a downdraft. This problem can be solved with a thorough chimney sweep.
  • Cracks in the flue system. The tiles or liner will need to be inspected for splits and openings.
  • Damaged or missing rain cap
  • The chimney opening is partially blocked by an object directly overhead, such as a tree.

A downdraft is not normal and may have safety implications. If the draft is accompanied by a smoky or musty smell, then bring in an inspector right away.

Other Causes of Chimney Downdraft

A downdraft may also be due to the improper construction of the chimney. Most local building codes require the chimney to be taller than any other part of the home. A roofline that’s higher than the chimney can affect wind flow and cause an inverted draft. In this instance, you many need to bring in a masonry expert to redo the chimney structure. At a minimum, the chimney needs to surpass the surrounding roofline by at least three feet. It should also be at least two feet taller than any other structure within a 10-feet radius. A taller chimney means a greater accumulated pressure differential, which will help prevent chimney downdraft.

We’ll Put a Stop to the Downdraft

Let Powers Chimney & Masonry fix the issue if you constantly experience a strong airflow coming out of the fireplace. A chimney downdraft can potentially be dangerous, so don’t let the problem go ignored.
Edited by Justin Vorhees

Chimney Inspection and Downdraft Prevention

Serving the communities of Arlington, Everett, Edmonds, Seattle, Mercer Island, Bellevue, Kirkland, Woodinville and all South Snohomish & North King County