Twin-wall flue systems, as the name suggests, are double-lined ducting systems that usually contain a layer of insulation between the walls to ensure the reduction of heat transfer.

Relatively low external skin temperatures can be obtained with twin-wall systems through the selection of the correct material grade and annulus thickness, depending on the flue gas temperature. A minimum 50mm clearance must be maintained from the outer skin to all combustible materials.

At A1 Flue Systems, we offer two specific types of twin-wall products:

• TF – this is a general-purpose chimney flue for use with gas- or oil-fired appliances
• HG – this is a high-grade twin-wall flue that can also be used for gas- and oil-fired appliances. It is the recommended option when a higher specification is required

Twin-wall flue systems are designed for use where:

• A four-hour fire rating is specified
• A negative-pressure exhaust/duct system is specified

Application examples include:

• Pressure jet burner
• Atmospheric burner
• Gas fires
• Flue dilution
• Ventilation/extraction

The complete range of A1 Flue Systems’ twin-wall chimney products has been successfully tested in accordance with B5476 Part 20 for stability and integrity during a four-hour fire test. They have also been CE Marked in accordance with British Standard (BS) 1856.

For technical help on twin-wall flue systems, download our product brochure. You can also either email our Technical Department at technical@a1flues.co.uk or call 01623 867303.

Also see Deltavent, A1’s own unique twin-wall flue system.