Balanced flue systems are room-sealed appliances, meaning that instead of using the air of the heating room as combustion air, outside air is supplied to the appliance. Balanced flue systems convey combustion air from the inlet above roof level to several heating appliances which are operated independently of one another. The flue gases are discharged via a separate duct above roof level. The flue liner and air supply duct can be arranged concentrically (duct within a duct with annular gap) or side by side.

Soot-fire-resistant balanced flue systems are also known as room-sealed chimneys and are designed for connection of heating appliances for solid fuels.

In accordance with the legal provisions of the federal states following Section 7(10) of the Model Firing System Ordinance (MFeuV), room-sealed heating appliances may only be connected to the balanced flue system if the construction technique ensures that they are suitable for this mode of operation.

These firing systems meet stricter tightness requirements and may therefore also be operated in highly insulated buildings, including in combined operation with ventilation systems.

Regulatory framework

In this work area, DIBt grants:

• national technical approvals (abZ) for balanced flue systems and/or parts of balanced flue systems that are not covered by a European Technical Assessment or the applicable harmonised standards for chimneys (system chimneys) or for parts of chimneys (custom-built chimneys);
• general construction technique permits (aBG) for the execution of balanced flue systems not covered by the execution standard DIN 18160-1.

National technical approvals and general construction technique permits can be granted together in a single decision ('combined decision').

European Technical Assessments (ETAs) can also be issued for balanced flue systems or parts of balanced flue systems that are not (fully) covered by a harmonised standard. For construction products covered by an ETA, a general construction technique permit for the application may be pertinent.

For dimensionally stable insulation products used in the execution of custom-built chimneys, voluntary verification (e.g. DIBt evaluations) is currently recommended if the application temperature limit for the insulation product lies above the flue gas temperature of the flue liners.

The technical rules to be observed in the execution of chimneys include:

• DIN EN 13384-1 – Chimneys – Thermal and fluid dynamic calculation methods – Part 1: Chimneys serving one heating combustion
• DIN EN 13384-2 – Chimneys – Thermal and fluid dynamic calculation methods – Part 2: Chimneys serving more than one heating appliance
• DIN V 18160-1 – Chimneys – Part 1: Design and performance

Please also note the relevant provisions of the federal states following MVV TB, Annex 8, Section 8.3 (2017/1) or Annex 14 (2019/1 and following).