Flue Liner Insulation

Flue Liner Insulation

Chimwrap is the ideal solution to insulating multi fuel flexible stainless steel chimney liner's. This unique and patented product manufactured in the UK, uses the most up to date technically designed products with ease of installation in mind.

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Gas & Oil

Gas & Oil

Stainless steel flexible flue liners are designed for lining an existing flue or masonry chimney. Gas and oil flexible flue liners are manufactured out of single strip 316 grade stainless steel and are designed for atmospheric gas and kerosene appliances where the flue gas temperature does not exceed 260°C.

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Stainless steel flexible flue liners are designed for lining an existing flue or masonry chimney. Multifuel flexible is a twin skin chimney liner designed for gas, oil and multifuel, where the maximum flue gas temperature does not exceed 600°C. There are two grades available, 316L and a higher grade of 904L which is suitable for the extreme conditions found with coal based solid fuel installations.

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Flexible Flue Liner


Document J of the Building Regulations requires that a flexible flue liner can only be installed completely enclosed inside a masonry chimney. A non masonry enclosure such as timber or plasterboard boxing is not acceptable. The type of flexible flue liner permitted depends upon the appliance and fuel type.  Gas and Oil flexible flue liners are manufactured out of single strip 316 grade stainless steel.

There are two grades of multi fuel liner available:

  • 316 grade stainless steel, which is suitable for wood burning and multi fuel use
  • 904 grade stainless steel, which is suitable for multi fuel and specifically coal based solid fuels

Prior to installation

The chimney should be inspected along with the external brickwork and capping/flaunching for deterioration and if necessary any remedial work should be carried out. The chimney should be swept, preferably by a suitably qualified chimney sweep who will provide a certificate after sweeping and checking, which should be retained for future reference.

Installation of the liner

The flexible flue liner can be pulled up or down the chimney using purpose made nose cones, which are available on request. For multi fuel liners, heavy duty and light aluminium nose cones can be supplied. lt is recommended that a coring ball or short test section is pulled through the chimney prior to installation in order to ensure the chimney is suitably sized, and free from any obstructions. We would always recommend that flexible flue liners are insulated to aid the performance of the appliance and chimney system. Insulation such as Micafil, K-Wrap or Chimwrap can be used. Please note that Micafil must not be used with gas liners.

Fuels and appliance operation

Only fuels which are HETAS approved or recommended by the appliance manufacturer should be used. If burning wood, it must be well seasoned for at least 12 months, and not contain more than 20% moisture content to avoid the build up of creosote deposits within the flue, which can cause chimney fires.

If the appliance is slumbered overnight or for longer periods then it is advisable to run the appliance at a controlled high fire condition for a period of at least 30 minutes. Prolonged slumbering of the appliance is a contributing factor to a flexible flue liner failure especially when burning coal based solid fuels. It is important to maintain sufficiently high flue gas temperatures in order to avoid condensate and acid corrosion problems.

Household refuse must not be burnt.


Provision should be made for inspecting and cleaning the flexible flue liner especially on multi fuel liners for solid fuel applications. The flexible flue liner should be swept at least once a year by a suitably qualified chimney sweep. Chemical chimney cleaners which contain chlorine, fluorine or metal scarifying devices cannot be used under any circumstances and will invalidate your warranty. Mechanical cleaning with a stiff nylon brush and rods are the only recommended methods.

Life expectancy

Under normal operating conditions and providing the flexible flue liner is installed correctly by a competent person, flexible flue liners should last the lifetime of the appliance.


Gas, Oil and 316 grade multi fuel flexible liners carry a 10 year conditional warranty, whilst 904 grade multi fuel flexible liners carry a 25 year conditional warranty.  However, the flexible flue liner must be correctly sized, installed, and properly maintained, burning only approved fuels in accordance with the appliance manufacturers instructions.


  • Flex


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