What is backfilling?
Backfilling refers to the method of filling the void between a flue liner and the inner brickwork of the chimney itself.
To backfill, a lightweight, insulating material is used, which comes in the form of small granules. The main types of insulation are Leca, Perlite and Vermiculite.
Why backfill a chimney?
Backfilling tends to be recommended for very cold chimneys, for example, external chimney breasts that are exposed to the elements. This is because even with a stainless steel flue liner, which has insulating properties, a very cold chimney can still affect the draw when burning solid fuel on a stove. If there is insufficient draw you will experience problems with lighting and maintaining a fire and condensation in the flue liner. This is because the hot gases released from burning will cool too quickly as they rise up the flue liner and instead of being released out of the chimney into the atmosphere, they will condense. The insulating properties of backfill material keep the flue supplieswarm, improving the draw and reducing the likelihood of condensation.
Is backfilling essential?
It is not a legal requirement, so it will be a recommendation of the installation company assessing your property. The majority of properties will not require backfilling; usually the flue liner itself is insulating enough and will sufficiently warm the air around the flue.
If you have any questions about this article or about flue systems in general, please contact us.
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