The purpose of the invention is to provide an insulation structure for efficiently controlling a thermal flow and protecting objects (6) that is easy to implement, has a low cost and is compliant with strict standards in terms of fire resistance while offering protection against crushing and immersion. Accordingly the invention relates to a method for protecting at least one object (6) previously encapsulated in a sealed pocket (4), that comprises imbedding the objects without trapping any air in a body of a high thermal-resistance insulator (2) containing gypsum crystals, said insulator body (2) being cast in a structure having a high mechanical resistance to crushing, and said structure consisting of an intermediate mould or directly defining a housing (1). A casing obtained by said method comprises the body block of a high thermal-resistance insulator (2) and the housing (1) having a high mechanical resistance to crushing. Advantageously, the objects, such as an electronic board, are encapsulated in a silicone sealed pocket (4), and the housing (1) includes steam discharge slots (10) as well as an opening (3) for casting the insulator body (2), said opening being then closed by a plate (12) held on the housing by screws (13). Sealed ducts are provided in the plate (12), the insulator (2), and the pocket (4) for passing electric wires (7) therethrough.