Chimney liners are required in a variety of situations.
Examples of situations in which a liner may be required:
- Wood inserts
- Wood stoves venting into a masonry chimney
- Oil or gas furnaces venting into a masonry chimney
Below are examples of acceptable and unacceptable wood insert installations.
Whether or not a liner is required can be a source of debate and disbelief. This is not surprising, as codes are not broadly published or well understood.
The code book which applies to chimney liners is the NFPA 211. NFPA stands for National Fire Protection Association.
Below is exactly what the code book says (2010 edition). What this means for wood inserts is illustrated in the picture to the left.
- There is a connector that extends from the appliance to the flue liner.
- Any unexposed metal that is used as a connector and is exposed to flue gases is constructed of stainless steel or other equivalent material that resists corrosion, softening, or cracking from flue gases at temperatures up to 1800 degrees F.
- The cross-sectional area of the flue is no smaller than the cross-sectional area of the flue collar of the appliance, unless otherwise specified by the appliance manufacturer.
- The cross-sectional area of the flue of a chimney with no walls exposed to the outside below the roofline is no more than three times the cross-sectional area of the appliance flue collar.
- The cross-sectional area of the flue of a chimney with one or more walls exposed to the outside below the roofline is no more than two times the cross-sectional area of the appliance flue collar.
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