In this paper, the influence of the vapor permeability resistance of insulated facades external facing on the moisture content was numerically studied. The calculations were carried out for the climatic conditions of regions with a continental climate with relatively cold winters and warm summers. The WUFI computer program was used to perform heat and humidity calculations. The calculations found that the moisture content of the insulation layer increases with a decrease in the vapor permeability of the external façade facing in the cold season. Thus, the calculations found that with an increase in the resistance to vapor permeability of the external facing Sd > 0.2 m, the average moisture content of mineral wool increases by more than 3 % in the winter period. To reduce the moisture content of insulation, a version of installing an interlayer vapor permeability retarder is proposed. According to calculations, the relationships between the vapor permeability resistances of the external facing and the interlayer retarder were established. The proposed approach using an interlayer retarder can be applied in the development of various designs of building facades with external insulation to protect the insulation layer from humidification during the cold season in regions with a continental climate.