Exterior wall chimney, which is called "double-walled" due to a mineral insulation layer around the flue pipe. The insulating layer, in turn, is covered on the outside with a metallic tube, usually made of high-quality stainless steel. As a rule, the chimney is routed along the façade over the roof.
The double-walled chimney is the predominant external wall chimney in residential and commercial construction in Germany. The thermal insulation prevents the exhaust gases from cooling, which improves the draught and reduces the amount of condensation. This makes the chimney, despite its location outside the building, relatively independent of the outside temperature. The double-walled chimney type is particularly suitable for fireplaces with room-air-dependent operation, as the system does not offer a general combustion air supply via the chimney. However, supply air intake via air openings in the area of the console or the connector that is still external is possible in the systems of many manufacturers.
Double-walled external chimneys are in principle suitable for all fuels, both in negative pressure and positive pressure operation. However, they require appropriate building authority approvals.
Source: bauwion
