A flue lining in a masonry chimney can be clay, ceramic, or metal, is intended to contain combustion products by directing them to the outside atmosphere, and protect the chimney walls from heat and corrosion.”
Although building codes vary from one state or locality to another, the installation of flue lining has been recommended since the early part of this century, and most fire codes now mandate liners.
Chimney liners serve three main functions:
- Protecting the house from heat transfer to combustibles. In unlined chimneys, heat can move through the chimney so rapidly that the adjacent woodwork caught fire in less than four hours.
- Protecting the masonry from the corrosive byproducts of combustion. If flue gases are allowed to penetrate into the brick and mortar, the result would be a reduction in the usable life of the chimney due to their acidic nature. This eats away at the mortar joints from inside the chimney. As the mortar joints erode, dangerous gases such as carbon monoxide can leak into the living areas of the home.
- Providing a correctly sized flue for optimum efficiency of appliances. Modern wood stoves and gas or oil furnaces require a correctly sized flue to perform properly.
Stainless steel liners work best with solid fuel (coal, wood, oil) based appliances while aluminum liners can only be used with gas appliances. Aluminum liners are very thin, inexpensive, can tear easily during installation, and tend not to last very long. Therefore, I install stainless steel chimney liners only. Stainless steel liners can be oval, round, or rectangular; and rigid or flexible. Flexible liners are much easier to install. Chimney liners are either 304L or 316L.
A chimney liner kit typically includes the chimney liner, a tee connector, a top plate, and a rain cap. The chimney liner diameter typically starts at 6″ and goes up from there.
If properly installed and maintained, these chimney liners are very safe.