Understanding how your chimney works


One of the most common complaints from fireplace owners is improper chimney drafting, or smoke entering the house from the fireplace rather than exiting through the chimney. The proper working of your chimney relies on the principles of physics. While it may sound complicated, understanding how your chimney works is really quite simple.

The physics of your chimneyUnderstanding the Machanics of your chimney - New Haven - Fairfield CT - Total Chimney Care

To understand how your chimney works, you first must understand that the air in your house is constantly moving. Warm air rises to the top of your home and attempts to force its way out of any cracks or crevices — including attic vents, light fixtures and cracks — it can find to reach the outside. At the lower levels of your house, cold air is attempting to get in to replace the warm air that’s exiting from the upper levels of your house. Somewhere in the middle, there’s the neutral pressure plane, the breaking point at which the air above is positive air trying to exit to the home and the air below is negative and trying to draw more air in.

Your chimney is part of your home’s circulatory system. When it’s full of warm air, as it is when there’s a fire in your fireplace, warm air rushes up the chimney while cool air is pulled into the fireplace. Any disruption in this system can interfere with your chimney’s ability to draft properly.

External disruptions to your chimney’s function

Believe it or not, any vented appliance in your home can affect the way your chimney is drafting. Appliances that draw air out of the house, including bathroom fans, kitchen hoods, clothes dryers and central vacuums, create negative pressure in the area of the fireplace. When there’s negative air pressure near the fireplace, that can prevent air from being draw into the fire and forced up the chimney, causing smoke to draft backward into your home.

Wind loading, when the wind outside is strong enough to put pressure on a portion of the house, also can disrupt your chimney’s draft. If the wrong portion of your house is pressurized by the wind, that can cause smoke to draft back into your home.

Internal disruptions to your chimney draft

One of the biggest culprits of a bad chimney draft is an improperly sized chimney. A chimney that is too tall or too short, too wide or too narrow can interfere with drafting and cause smoke to flow back into your home. Closed or jammed dampers can interfere with the chimney’s draft. Creosote can block your chimney, and your chimney flue or chimney cap can be plugged with debris that prevents your chimney from drafting properly and causes smoke to enter your home.

If you’re having problems with your chimney’s draft and suffering from an influx of smoke into your home from your fireplace, call the chimney experts at Total Chimney Care. We’ll inspect your fireplace and chimney, and help you identify and rectify the problem.