Chimney cleaning is one of the most important ways to keep your chimneys in good condition. Besides regular cleaning, one shall also install a chimney liner in order to maintain the chimney properly. A flue lining in a masonry chimney is a clay, ceramic, or metal conduit installed inside of a chimney, intended to contain the combustion products, direct them to the outside atmosphere, and protect the chimney walls from heat and corrosion. Although the structures differ from place to place, the installation of chimney lining has always been recommended and most fire codes now mandate liners.Chimney liners are used due to three major reasons
- A) The chimney has no clay tile chimney liner (older chimneys may not)
- B) The clay tile chimney liner is damaged
- C) For optimal performance and safety because you are installing a new heating unit (stove or furnace) that will be vented into your masonry chimney.
Older chimneys tend to be less efficient with respect to their furnaces and therefore a chimney liner is not needed. This is so as the steam released by such furnace can be up to 700 degrees Fahrenheit and therefore, steam uses the entire space of the chimney while travelling up. Efficient furnaces, such as those at 80% AFUE, also use the chimney for ventilation. Steam released by them has a lower temperature of 400 degrees Fahrenheit.
Hence, a chimney liner is inserted into the chimney to reduce the space avoiding moisture that could build up along the sides of the chimney if steam does not use the whole space inside the chimney. This could lead to chimney destruction as the acid might seep into the mortar.
You do not need a chimney liner, if you already have a chimney liner. You can check it out by having a quick look at your chimney. If you find a metal pipe or top coming out just over the top of your chimney, then it is likely that you have a chimney liner already present in your chimney. If your furnace is very old, it might be inefficient and would not need a chimney liner.
Steam from highly efficient furnaces (90% AFUE and above) is too low for even a chimney liner to work. Hence, such units need a different ventilation system consisting of PVC pipes.
Generally newer homes have chimneys that are thin and made of metal. They are already ready for more efficient furnaces that need a smaller ventilation space.