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What is a Flue

For any stove or fire to work successfully, it must be connected to a sound chimney and a correctly sized flue. A chimney works because hot air rises. Factors such as running the appliance at a very slow rate or cold air leaking into the flue, will cool down the gases and affect the performance of the chimney. An efficient wood burning stove produces flue gases that are cooler than an open fire. For this reason it is necessary to install an insulated liner within an existing chimney when a wood burning stove is installed to ensure that there is a sufficient draw of air. If there is no existing chimney it is possible to install a wood burning stove by constructing a twin walled flue using one of the proprietary systems.

Flue-Liners

Since 1965 houses with chimneys have been constructed including the chimney liner. This was usually done with a clay liner which should last the life time of the building, although this may not be the case due to poor installation standards. Prior to 1965 lining was less common and chimneys were usually rendered with a lime mortar. Most old chimneys need to be relined before they can be re-used, particularly those that were built without a lining or have a flue that is too big and inefficient for modern stoves and fires.

Do Not Allow Creosote to Build Up In The Chimney

Creosote is a highly combustible substance which condenses in liquid form as wood exhaust cools in the chimney, and then solidifies as it dries. If ignited, creosote can burn for days at temperatures exceeding 2,000 degrees, which is hot enough to destroy the chimney and ignite surrounding combustibles. Creosote is very caustic; if allowed to accumulate, it will significantly shorten the lifetime of the stovepipe and chimney. A seasoned-wood fire that is given enough oxygen for proper combustion will reduce creosote formation in two ways, by consuming more of the wood gases while at the same time sending more heat up the chimney to reduce flue gas cooling.

Practice Proper Chimney Maintenance

Creosote should be removed from the chimney before build-up in the flue exceeds 1/4" thickness. Chimneys which vent properly operated woodstoves generally require cleaning twice per year. If green or wet wood is burned, or if the fire is allowed to smoulder, the chimney will require cleaning much more often, and should be inspected frequently. Creosote sticks like glue, and must be removed with a tight-fitting steel brush. Rattling tire chains down the chimney or pulling a bag of straw through the flue won't remove creosote, and neither will a chimney fire. Chimney fires burn away the resinous portion of the creosote, but the sooty husk remains: if this husk isn't removed after a chimney fire, smoke will filter through it, rapidly re-depositing fresh liquid resin. In a very short time, the chimney will be as bad as it was before the fire.