In this paper the assessment of moisture conditions of four types of walls with façade’s thermo-insulation composite systems with external mortar layers is executed. It is shown that for wall products from AAC algorithm of calculation of the maximum moistening interface according to the Russian norm SP 50.13330.2012 “Thermal protection of buildings” yields physically unreasonable result and needs adjustment. It is necessary to distinguish the concepts “maximum moistening interface” and “moisture condensation interface” defining various physical processes in the building components. The calculation of protection against remoistening of the building components executed according to basic method SP 50.13330.2012 has shown that systematic accumulation of moisture in the building components during the annual period is absent; remoistening of heat-insulation layer during moisture accumulation period is absent also. The device of an additional vapour protection layer in this constructions isn't required. Calculation of moisture conditions of the building components by alternative method in the annual cycle has shown that in all considered types of the structures the moisture condensation interface in the coldest month of year is absent. In this case condensation of moisture in the building components is absent. Duration of drying of external walls from AAC increases when using as external heat-insulation layer made the plates from extrusive expanded polystyrene having low vapor permeability. For normalization of moisture conditions of walls initial moisture have to be removed from the building components within 2–3 years from the moment of commissioning of the object.