Insulation of an external chimney from a sandwich pipe in a metal profile box

Good afternoon.

I ask you to consult on the device of an external chimney of a fireplace. The question is: the external chimney itself is made of a sandwich pipe with a diameter of 200, a steel thickness of 0.8 mm and a heater of 50 mm (basalt) of factory manufacture. According to the architecture of the house, we beat it with a decorative box 1200 * 600, made of a metal profile for the installation of finishing panels. The facade of the house is ventilated from KMEW fiber cement panels. Tell me whether it is necessary to insulate the space inside the box over the entire height of the structure (8 m) between the panel and the sandwich pipe. If so, what would you recommend. Thank.

Oleg.

Hello Oleg.

The chimney from the sandwich pipe is a self-sufficient structure and does not need additional thermal insulation. However, its insulation will create an atmosphere inside the box, which will contribute to the safety of other materials. The fact is that, despite the 5-cm layer of insulation, the pipe will be warm outside. In the cold season, even a small temperature difference inside the decorative box can contribute to the formation of condensate. By installing an additional layer of thermal insulation, you can shift the dew point outside and thereby ensure the safety of the facade. As for the choice of material, here the simplest roll or plate thermal insulation of mineral origin is suitable - basalt cotton wool, glass wool, etc.