How Your Home’s Chimney Actually Works

Chimneys and fireplaces, warm and cozy; but do you know how to tell if it is working properly. It may seem like a complicated operation, but the basic physics of how a fireplace and chimney work are relatively easy to understand. Here are some quick tips so you will be able to tell if your fireplace and chimney are working safely and properly when in operation.

Ashbusters Chimney - How Your Chimney Works

  • Think of your home as a flow system, where air enters in the bottom and escapes through the top. The airflow of the home is influenced by a variety of factors, including the operation of your fireplace.
  • When warm air is created, it rises in the home. This is sometimes referred to as the “stack effect.” This warm air is trying to escape in any way it can, be it a chimney or crack in the window molding. While this air is trying to escape, colder air is trying to get in. The Neutral Pressure Plane, or NPP, establishes itself somewhere in the home dictating the point where air begins to escape and enter. The areas below the NPP are entry points and the areas above the NPP are exit points.
  • Wind will also affect the operation of your chimney. When wind hits a building, this causes a high-pressure build up. Downwind, the side of the home away from the wind strike, experiences a low pressure. If there is an opening on the downwind side of the home, it will depressurize the home and can cause a backdraft in the fireplace or chimney, thus resulting in smoke coming into the home.
  • Other mechanical devices in the home will also affect the performance of your chimney. Appliances and such creating a vacuum or forcing air can make it very difficult for the chimney to perform properly as they are changing the natural flow of air in the home.
  • Airflow can be restricted in your chimney as well from a lack of preventative maintenance. For example, a wood burning fireplace may experience excessive creosote buildup, leaving a smaller area for the smoke to flow. In addition, this is a major fire hazard. This flow can also be interrupted due to dirty or obstructed dampers, screens, and chimney caps.
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