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For a stove to work successfully it must be connected to a sound chimney and properly sized flue.

The purpose of a chimney is to remove the products of combustion from the appliance to the outside without causing harm to the occupants or risk of setting the house on fire.

A chimney works on a simple rule hot air rises therefore the flue should be well insulated for this to happen.

Before going any further it is important to understand the terms that are used.

  1. CHIMNEY - This would be the structure surrounding the flue/flues.
  2. FLUE - The flue is the passageway which the products of combustion travel to the outside from the Stove, furnace, hot water heater, fireplace or any other heating appliance.
  3. FLUE LINERS - Is the material used to form the flue.
  4. THE THIMBLE- The terra-cotta or metal pipe that passes thru the wall.
  5. STOVE PIPES - The pipe connecting from the appliance to the flue inside the chimney.

Operating a stove at a low temperature for long periods or cold air leaking into the flue, will cool the flue gases down and affect the performance of the chimney. To keep the flue gases warm, proper thought must be given to the insulation properties of the lining within the chimney.

Before flue liners were ever manufactured flues were usually parged on the inside with mortar. This parging over a period of time would have deteriorated from the corrosive properties within the flue gases, resulting in deteroration and leakage. This can usually be noticed by a sandy-powder like material falling down inside the chimney .That sandy material would be the plaster that has deteriorated over a period of time also the mortar between the bricks will have deteriorated in the same way.

Chimneys are often constructed on the outside of the house and are exposed to the elements. This combined with the fact that there might be no insulation around the flue liners all adds up to a cold flue.

Remembering that stoves are efficient heating appliances and will produce up to 80% of heat from the fuel being used into the room, not like an open fire that can loose up to 75% of the heat. With little heat loss from an efficient stove it becomes understandable how important it becomes to maintain a reasonable flue gas temperature in order to achieve the proper draft.

A properly lined and well insulated flue will produce a safe and efficient appliance. Unlined chimney flues can result in very costly rebuilding of the chimney and/or your home.


There are a number of reasons why a chimney should be lined or relined:

  1. Creosote or moisture are seeping through the chimney walls causing staining on the outside or inside the building.
  2. The flue is too large for the type of appliance being vented.
  3. The flue is leaking smoke and carbon monoxide into rooms or parts of the building.
  4. The flue is too cold. Especially if it is on the outside wall, and not drawing properly.
  5. The chimney is old and was build before flue liners were ever manufactured.
  6. The flue liners are cracked due to a chimney fire. Causing leakage.
  7. The flue liners were never installed properly. There are gaps in between the flue liners