The concept of thermotechnical calculation of external enclosing structures of buildings is presented, based on the fundamental processes underlying the thermotechnical design of building elements, as well as on the current building codes of the Russian Federation. The basic concepts related to thermal engineering calculation and formation of the internal microclimate of premises, as well as the principles of its provision using engineering systems are considered. Methods for assessing the humidity regime of enclosing structures and its effect on heat transfer through them are given. Assessment of microclimate comfort is given and rules for selection of its permissible and optimal parameters are given.