A flexible heat-insulated conduit is described, made up of at least one medium-carrying internal tube, an external tube surrounding the at least one internal tube, and a heat-insulating layer based on polyurethane foam or polyisocyanurate foam and located between the at least one internal tube and the external tube, in which 0.1 to 7.5% by weight of hollow spheres are added into the foam, the hollow spheres comprising a casing made of a thermoplastic and being filled with a medium that brings about an inflation of the casing at an elevated temperature.