Chimney

• How can you tell if a fireplace will draw properly without lighting a fire?
  • Fireplace draw is dictated by the design of the fireplace, however, there are critical specifications that carry considerably more weight when you are trying to determine whether or not a fireplace will draw.
  • The two most significant criteria are the height of the chimney as it relates to the roof and the size of the firebox in relation to the flue.
  • Chimneys must extend at least 2 feet higher than any portion of the roof or any structure within 10 feet, but must be not less than 3 feet above the point where the chimney passes through the roof.
  • The flue must be 1/12 the size of the firebox opening, or larger. If the flue is 8'' x 12'' (approximately 96 square inches) and the firebox opening is approximately 30'' x 32'' (960 square inches), the flue is determined to be 1/10 the size of the firebox, indicating that the fireplace is very likely to draw properly.
  • Although there are other important concerns, if the above 2 items are correct, the likelihood that the chimney will draw is high.
  • Read more in-depth information about chimneys and fireplaces.
• How can you tell a chimney is blocked without looking up or down the chimney?
  • If the heating appliance is operating, there will be an excessive amount of heat and moisture backing out of the draft hood (gas-fired) or draft control and view door (oil-fired). This would be obvious to a casual observer.
  • If the heating appliance is not on, such as during the summer months, and the chimney is blocked, there will be rust debris at the draft hood (gas fired) or excessive soot at the draft control and view door (oil fired). If the blockage has accumulated over a long period of time, the rust build-up would be excessive.
  • The exhaust from the appliance combustion is approximately 90% water, which will
    cause oxidation and rust at the draft hood. When the unit is operating, the relative humidity in the area of the heating appliance can reach 100%.
    
  • Read more in-depth information about chimneys, fireplaces and wood stoves.

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