What is a Chimney Liner and What Function Does it Perform?

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Chimney Cleaning and Sweeping

The chimney liner is known by a couple of different names; chimney liner and chimney flue. So if I use both of those terms often, it’s because they’re completely interchangeable. The flue is available in a variety of materials, and performs an extremely important function in the grand scheme of things. Today I’m going to explain the functionality of the chimney liner and describe three different types that are available to all homeowners who use their chimney.

The Functionality of a Chimney Liner

A chimney liner, or flue, is the lining inside the actual chimney. The chimney itself is the structure that sticks up out of the roof. Now that we have that quick description out of the way, let’s talk about the actual functionality of the chimney liner.

Protects the home from heat transfer to combustible structures. Homes are constructed from wood. Wood is a combustible. The flue absorbs heat so it is not transferred to the wooden supports that hold the roof in place.

Protects the masonry chimney from corrosive byproducts. The byproducts of combustion are very corrosive and will chip away at masonry over time. This weakens the structure of the chimney, and will eventually lead to chimney collapse.

Increases efficiency of fireplaces and wood stoves. Fireplaces and wood stoves require an appropriately sized flue in order to burn efficiently. An ill fitting flue leads to faster creosote buildup and increases the buildup of carbon monoxide.

Types of Chimney Liners

Chimney liners are available in three primary material types: clay, metal, and cast in place. The type doesn’t really matter, as long as it is professionally installed, inspected, and cleaned on a regular basis. Always make sure to follow manufacturer’s instructions and local building codes when installing a chimney flue.

Clay Tiles: Relatively inexpensive, readily available, and maintain a pretty good performance record. The two disadvantages to using clay tile chimney liners is that they do not evenly absorb heat during rapid temperature increases, and they do not adequately absorb liquid combustion byproducts produced by gas appliances. Due to these two disadvantages, they may crack or shatter, rendering them completely useless and in need of replacement at any given time.

Metal: Usually stainless steel or aluminum, they are a nice upgrade for modern chimneys. They are very durable and relatively inexpensive. Stainless steel is a little more expensive than aluminum, and stands up to higher heat more effectively than aluminum as well. You should have a good idea of the heat efficiency of your fireplace or stove before deciding between stainless and aluminum.

Cast in Place: Lightweight, cast cement-like product that is, as the name suggests, cast in place inside your chimney. They improve the structural integrity of older chimneys, and are considered a permanent liner, suited for all fuel types.

Unlined chimneys are a fire risk; please do not attempt to burn wood or any other substance in your fireplace or wood stove in an unlined chimney. Doing so puts your home and the health of the occupants at risk. Call me for a consultation, inspection, cleaning, or installation of a chimney flue if you’re in the Philadelphia area.

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