Moisture is a big problem for outer walls in Russia since it causes destruction of buildings and structures. The objects of investigation are outer walls from autoclaved aerated concrete blocks (AAC) for apartment residential buildings located in various climatic zones of the Russian Federation. The calculation of moisture conditions of outer walls is extended by two ways: by simplified method (according to National Standard SP 50.13330) and specified method on the basis of the analysis of moisture conditions of enclosing structures in an annual cycle. Calculations showed that, there is not a critical repetitive moisture accumulation on the layers of the wall, the placement of an additional vapor barrier layer in designs isn't required. The functional dependence of the specific heat-insulation characteristic of a building on humidity of AAC in outer wall is defined. The criterion of remoistening of AAC in outer wall based on the admissible operational humidity is formulated. The results of investigation allow estimating more precisely moisture conditions of AAC at design of buildings.