Abstract: It is illustrated a joint system (1; 1?) for joining end portions (2; 2?) of at least one panel (3; 3?) made of pre-insulated material comprising a joining device (4; 4?; 4?) provided, at opposite parts of a longitudinal centreline plane (?) of the same, with a first (5; 5?; 5?) and a second (6; 6?; 6?) longitudinal seat, each of said seats (5; 5?; 5?, 6; 6?; 6?) being adapted to house one of said end portions (2; 2?) of said at least one panel (3; 3?), said joining device (4; 4?; 4?) comprising means (8; 8?; 8?) for being fixed to the panel (3; 3?) adapted to be engaged in a removable manner with respective fixing countermeans associated with said at least one panel (3; 3?).