The technical field of the invention is the fabrication of boxes or other package volumes which are foldable and may be transported, when empty, in a minimum space: the present invention relates to such parallelepipedic boxes comprising a base (7), four side faces held to the base by means of a flange (10) and of which two (5) are opposite to each other and connected by lateral foldable elements, allowing to bring face to face said two walls (5), once detached from the base (7), and a cover panel (4) intended to top and hold, at the opposite of the base (7), said side faces; the two side faces (5), which are interconnected, are insulating rigid panels, the two side elements which connect them are belt portions (6), and the two other opposite faces (4) are also independent insulating pannels which are inserted between the two first faces (5) and against said belts (6), when the latter are unfolded.