The invention provides a mounting screw (100) for fastening fitting parts, particularly hinge parts onto a chamber profile, which comprises a threaded part provided with an external thread. The length of the threaded part is greater than the spacing of two adjacent walls of the chamber profile. The mounting screw comprises a front part (1) and a rear part (2), as viewed in the screwing-in direction. The front part comprises an external thread (3) and is preferably made of a metallic material. The rear part is made of a thermally insulating material, for example plastic. The outer wall of the chamber profile is only in contact with the adiabatic rear part of the mounting screw.