Energy efficiency building envelopes (walls, floors, facades) should meet the requirements of regulatory documents. The main attention is paid to structural and technological activities aimed at increasing the thermal resistance of protections. Estimates of the thermal stability of the wall are required for realization of high thermal resistance of the wall structure. The object of study is a simple model of the building envelope. It has been shown that the increased thermal conductivity, thermal resistance does not always provide the steady-state temperature faces the wall. Research method is based on the analysis of the properties of the Cauchy problem. In this article it is found out the connection between the active (thermal resistance) and reactive (accumulation) resistance enclosure on the model of one-dimensional wall.