Regulations for Gas Heat Chimney Liners

Material

• Only certain materials can be used in gas chimney liners, although materials used in most home chimneys are acceptable. Materials allowed in any home fireplace include: clay flue lining, firebrick lining, factory-built chimneys or chimneys listed for installation within masonry chimneys. Some liners are approved specifically for use with gas chimneys and should be labeled that way by the manufacturer.

Vents

• Gas chimney liners should also have approved vents. The National Fire Protection Association recommends type B vents listed for installation within masonry applications, but will allow special gas vents listed for installation within masonry chimneys. When some types of vents are used as liners, this must be clearly indicated by a label that attaches to the wall or ceiling where the connector meets the chimney.

Installation

• The material you use for your chimney liner will determine which installation guidelines you must follow, according to the National Fire Protection Association. Fireclay flue liners should be installed ahead of the construction of the chimney as it is carried up. They should be bedded one on the other in a medium-duty, non-water soluble calcium aluminate refractory cement mixture, or its equivalent, with the joints left smooth on the inside. Portland cement-bonded mixtures should be avoided. Fireclay brick flue liners should be installed with full-width refractory mortar. Fireclay flue lining should be separated from the chimney wall by .5 to 4 inches of air space. The liner should start at or below the base of the chimney flue and should be supported by solid masonry, carried up as vertically as possible, extending to the entire height of the chimney to at least two inches above the crown, splay or wash. Finally, the crown, spray or wash must be constructed to allow for unrestricted vertical movement of the liner due to thermal expansion, without allowing moisture into the chimney.