In the time when sustainable construction as well as cost saving on heating and cooling of buildings is one of the most important construction trends, it is important to acknowledge the possibilities of application of construction materials with high heat insulation parameters and the ways in which these parameters can be obtained. Autoclaved aerated concrete (AAC) is a load bearing construction material, which has high heat insulation parameters, although it has one significant disadvantage. If the AAC masonry construction has high moisture content, it loses its heat insulation properties. This is the reason why it is important to detect the humidity distribution throughout the cross section of the masonry elements in order to conduct the drying process of the AAC construction. Therefore, the question about non-destructive detection of humidity distribution throughout the cross section of the material arises. Humidity distribution throughout the cross section of AAC masonry constructions has a significant impact on its heat resistivity properties. Application of electrical impedance spectrometry (EIS) method for determination of humidity distribution throughout the cross section of AAC constructions has been a subject of research recently. The EIS method is an easily applicable non-destructive testing method for detection of the humidity distribution throughout the cross section of a construction. Research on the impact of the external heat insulation layer on the speed of humidity distribution changes is described in this paper.