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Twin Wall Flue Systems

If you wish to use a stove but do not have a chimney then this is the solution. Our twin wall double skinned stainless steel flue pipe is suitable for the construction of internal and external flue systems, the twinwall is suitable for multifuel and woodburning appliances.


Twinwall Insulated Flue Systems for multifuel, wood burning and gas appliances

Twin wall insulated flue is suitable for constructing internal and external flue systems for wood burning stoves, multifuel stoves, gas and high temperature oil stoves. Our twinwall flue pipe is a double skinned flue that is approved by the latest HETAS official guide for approved solid fuel products. Our twin wall insulated flue pipe is made with an inner layer of 316 grade stainless steel a 25mm insulation section of rockwool and a outer layer of 304 grade steel.

Twinwall Flue Pipe

A twin wall system

Outer layer

The outer layer of the flue may pass within 50mm of combustible materials, this makes it accommodating to install in existing houses, it is also weatherproof and carries the structural load of the flue system.

Rockwool Insulation

The 25mm of high density mineral Rockwool between the layers of twin wall flue pipe has thermal resistant properties which keeps the external of the flue cool, this ensures the gases stay warm and rise up the flue, this reduces deposits of tar on the internal of the flue that is often the main cause of chimney fires.

Inner layer

The inner layer is made of 316 grade stainless steel and is able to withstand corrosive flue gases given off by wood and coal burning stoves. The inner steel heats up rapidly to produce a strong draught which ensures that waste gases are exhausted up the flue, the steel can also contract and expand as gas temperatures change throughout the burning of the stove.

General Help & Advice

Twinwall flue systems should be installed with the minimum amount of horizontal turns and offsets. For solid fuel appliances the distance between two 45 degree bends should not surpass 20% of the vertical flue height. The flue size of the twin wall system should never be reduced to less than the flue diameter on the stove, often stove manufactures recommend an increase in the flue diameter.

All lengths and offsets connect together using a locking band system which seals the flue and prevents any leakage, no joints should be made in walls or going through floors. Access must be made for sweeping and inspection purposes these are generally found in Vitreous enamel pipes with sweeping hatches or in 135 degree twinwall insulated Tee & Caps.

For the Flue system to work correctly you must ensure that adequate air is available for combustion, for full details refer to Document J Building Regulations.

All Flue systems must have enough support there is a range of support brackets that are available adjustable and fixed, we recommend a support bracket every 2m.

To go from Vitreous enamel flue pipe to Twinwall insulated flue pipe a special adapter is required which seals the joint and also allows you to increase the diameter of the flue. We recommend in a flue system you increase the flue diameter, this is the case for all flues i.e liner, as this increase helps the draw on the flue which enables it to function more efficiently.

When a double skinned twin wall flue system needs to travel 45 degree diagonally through a vertical wall an adjustable twin-wall length is often required. This twin wall length is usually adjustable as it is difficult to measure wall thickness. The Twin-wall adjustable lengths come in two different sizes the smaller of the two is 250mm - 450mm and the larger is 500mm - 950mm. Whilst going through a wall the gap between the adjustable twinwall flue pipe and the wall itself is generally packed out with vermiculite to prevent any condensation but always consult your HETAS qualified fitter for any installation details and up to date regulations.

Our Free Twinwall Design Service

Height Twinwall Flue Exits

Clearance heights of the flue outlets.
A = Must terminate at least 600mm above the ridge.
B = Must terminate at least 2300mm from the nearest point of the weather surface (at least the height of the ridge or 1000mm above the highest point of the inter-section).
C = At least 1000mm above the top of the opening.
D = At least 600mm above the ajacent building.

Please note:

  • The weather surface is the the buildings external surface such as its roof tiles.
  • A flat roof has a pitch of less than 10 degree.
  • The clearances given in A & B apply to a flat roof.

We offer a FREE Twinwall design service, use our really easy and simple form - click here, or email or fax a drawing of your requirements to us. Our twinwall experts will select all the relevant components required and will get back to you with a breakdown and price - no obligation.

Please contact our technical team using any of the following methods including your diagram, name and contact numbers all clearly marked. When emailing or faxing a diagram please ensure you include the following dimensions:
Overall height, flue outlet size on the stove, wall thickness (if applicable), height to each ceiling, loft space and roof angle.

E-mail: online@stovesareus.co.uk

Fax: 01484 773170

Phone: 01484 434320

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