In this paper we propose a method for determining a combination of layer thicknesses ensuring the predetermined maximum allowable temperature at the layer boundaries provided that the number of variable layers is not equal to the number of controlled points. We present a numerical example of solving the problem of designing a three-layer structure subject to bilateral heating, with the requirement that the maximum temperature of the construction inner layer should not exceed 1073 K. This requirement is satisfied by varying the thickness of the outer thermal insulation layers. The solution obtained by using the developed method, asymptotically approaches the optimal solution in extreme setting of the problem.