Hygrothermal conditions in innovated autoclaved aerated concrete (AAC)-based building envelopes are studied in the paper, using computational analysis with exactly measured hygric and thermal transport and storage properties as input parameters. The applied computational model of heat and moisture transport in multi-layered systems of porous materials is based on the Galerkin finite element approach. The computer code written in C++ is used in a series of computational simulations. Climatic data corresponding to the test reference year for Prague are used as boundary conditions, so that cyclic wetting and drying occurs in the envelope. The results of computer simulations of moisture and temperature fields are then utilized in the subsequent service life analysis. On the basis of changes of moisture and temperature, particularly the number of wetting-drying cycles and frost cycles the durability of the AAC envelopes is assessed.