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Insulating a chimney flue

Insulating a chimney flue


Insulating a chimney flue is important to maintain the safety of your home and family when you use the chimney.

Reasons to insulate flue

Sudden temperature changes can damage the chimney, and cause cracking or even breaking of bricks or even concrete. Insulating the flue means reducing the moisture amount that comes down the chimney and reaches the heat source.

A chimney can be damaged and can even collapse because of the mortar being eaten away by dampness.


Lime or sand are used in the first insulating step. The process of spraying lime or sand onto the freshly drying mortar inside the chimney is called parging. It is done to reduce the containment of gasses that come from fires and makes them rise instead of passing through gaps in the mortar.


After you are done parging the inside of the chimney, you must install one of the 3 types of liner: cast concrete, solid sectional liner and metal liner.

Cast concrete liner

To install a cast concrete liner you must first insert a rubber tube down the flue and then, place concrete blocks into the chimney stem every 2 meters. The heat transfer is reduces but so is the air draft.

Solid sectional liner

These liners can be build in while the chimney is restored. The sectional liner is made out of terracotta clay or concrete and is mostly used in large and wide chimneys that follow a straight path.

Metal liners

Large open flues of wood stoves use stainless steel metal liners. These liners are attached to the chimney flue with clips. The gap between the liner and flue needs to be filled with vermiculite or another granular material. Used on any type of flues, double-skin liners can be quickly installed, repaired and removed. Closed stoves and boilers use only gas flex liners.

Chimney flues insulation are of many types. Search for the proper one for your chimney.

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