We investigate the maximum wetting plane position in two enclosing structures: the first enclosing structure is with aerated concrete base and mineral wool insulation, the second enclosing structure is with aerated concrete base and expanded polystyrene insulation. Two fundamentally different cases of the maximum wetting plane are obtained. For the enclosing structure with mineral wool insulation, the maximum wetting plane is located between the insulation and the external stucco. It was found that when the indoor climate parameters or thicknesses of layers change, the position of the maximum wetting plane does not change. For the enclosing structure with expanded polystyrene insulation, the maximum wetting plane is located inside the insulation layer. It was found that when the indoor climate parameters or thicknesses of layers change, the position of the maximum wetting plane also changes. In terms of application result for calculation, an enclosing structure with aerated concrete base and expanded polystyrene insulation is significantly more sensitive to climate parameters than an enclosing structure with mineral wool insulation. It becomes possible not to obtain the maximum wetting plane position in encloses with mineral wool, and to use described calculated position, therefore, it can save time of engineers during the moisture regime calculation.