Introduction

The most appealing focal point in any room must be the fireplace. Be it an open fire, closed stove or roomheater, the leaping flames and glowing coals are the real heart of the home.

However, for any fire to work successfully, it must be connected to a sound chimney and correctly sized flue. The functions of a chimney are to safely remove the products of combustion from the fireplace or appliance to outside without causing danger to the occupants of the house or setting the house itself on fire. A chimney works because hot air rises and always moves from high to low pressure. Factors such as running the appliance at a very slow rate or cold air leaking into the flue, will cool the gasses and affect the performance of the chimney. To keep the flue gasses warm, consideration must be given to the insulation value of the lining system chosen.

In houses built since the introduction of the 1965 Building Regulations, all flues must be built with liners during their construction. This is usually done with clay liners, which should last the life of the building. However, in houses built prior to 1965, lining was less common. Flues were usually “parged” (rendered) on the inside with lime mortar. This parging suffers attack from acids and tars produced during combustion, and gradually deteriorates. The flue is then in poor condition, often leaking fumes or tars into the walls or other parts of the building. Sadly, many houses built since 1965 suffer similar problems due to badly installed flue liners and need further attention.

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