Abstract: In a heat-insulating structure conisting of stacks of metallic modular elements placed in imbricated relation by means of overlapping edge portions, each stack is assembled by means of a single fastening member which is passed right through; and each modular element comprises a leak-tight chamber divided into two equal compartments having the shape of right-angled parallelepipeds, overlapping edge portions formed by the compartments which are relatively displaced along one diagonal, a spacer member fixed between the large bearing faces of the chamber and a filling structure within each compartment.