Abstract: Heat-insulating pipe element of a pipe for conveying flue gases comprising a metal outer tube, a metal inner tube fitted co-axially in the outer tube by fixing means in a substantially immovable relation to the outer tube and a heat-insulating material being provided in the space between the tubes, whereby the fixing means comprises at least one elongate connecting element which is provided in longitudinal direction between the tubes and of which the extremities are connected with the respective end parts of the outer tube of which the central part is connected with the central part of the inner tube, and whereby the fixing means also comprises the insulating material, in the form of a continuous insulating layer, having a coherent, fibrous resilient structure.