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Conventional and Balanced Flue Systems

Conventional Flues

Conventional Flues are the most common type of chimney installed, mainly traditional brick. They work by pulling the warm air rising up out of the chimney away considering that air is passing over the top of it. This pulls air from the room through the fire/stove and up into the chimney. Conventional flue chimneys terminate in clear air 2.4m away from anything or 600mm above the ridge of the roof.


Different types:

  • Class 1 – Brick built or clay/ concrete lined traditional chimneys opening to a fireplace at the bottom.
  • Class 2 – Prefabricated metal flue systems added to a property that has no chimney. Connected directly to a stove/fire than opening up into a fireplace.

Wood Burning, Multifuel and Pellet Stoves are conventional flues. Gas Stoves/ fires can work on both flue types but are normally bespoke made. Conventional Flues might need lining if the property of a certain age.

Balanced Flues

Balanced Flues only apply to gas stove/fires. They are constructed of one pipe inside the other. The inside pipe removes waste gasses and the other brings air for conbustion. Balanced flues are commonly known as concentric flues and are not twinwall flues. Balanced flues do not require any additional air from the room and so all stoves/ fires will be glass fronted or have a closed door that cannot be opened. They are room sealed.

Flavel HE Balanced Flue Drawing


  • Heating Efficiency – They bring in fresh air from outside, more oxygen is available to mix with the gas for complete burning.
  • Not restricted to a particular chimney size – They can work with or without a chimney.
  • Can be fitted to a ceiling or wall – Depending on preferences or room requirements.


  • Fire behind glass – Some people do not like the aesthetic visual appeal of this.
  • Glass can become scorched – With not very good upkeep or servicing.
  • Fire surround consideration – High temperatures generated by the fire.

These flues do not get as hot as conventional flues and they do not need to be run as high as conventional flues. Instead all you need is an external wall, where you can either come direct out the back of the appliance, through the wall and terminate, or rise up, bend 90° through the wall and terminate at a higher level.

So, if you have no chimney in your home, or if you are looking to place a fire in a room that either has no chimney or the chimney is not where you would like to place the fire, then a balanced flue could be the perfect option for you.


Flueless is an alternative to a conventional or balanced flue. Electric, bio-ethanol and gas do not require a chimney to run. Gas stoves and fires feature a catalytic converter built in to them that burns off all the waste gases, meaning that it does not emit any fumes back into the room and as such requires no flue.

Converting a Conventional Flue into a Balanced Flue

Chimney Renovation Kits allow you to convert conventional flues into a balanced flues. These special kits provide a concentric pipe off the top of the stove/fire into the chimney where they will seal into a special register plate.

One comment

  1. Brian Lawn

    I have a Neston Baton LPg fire with conventional flue which I now wish to use now in accommodation without a chimney and therefore need a balanced flue. I found your article very interesting and relevant. Where can I buy a conversion kit, I have found many chimney liner kits but no conversion. Have you any idea of cost. Thank you

    Where does one buy a kit to convert from conventional to balanced flue.

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