One of the basic principles of energy efficient buildings in accordance with sustainable development is perfectly airtight building envelope. Oversized heat losses through the building envelope leakage adversely affects the energy balance of buildings. The quality of airtight building envelope except for low energy consumption also minimizes the risk of damage to the structure associated with the spread of the heat and water vapor in the structure. The contribution provides diagnostic of the contemporary development in airtightness of buildings using by qualitative methods. The aim of contribution is to draw conclusions - dependences, definitions of weak and strong points of the process, their causes and consequences. It is necessary to pay attention to the determinative factors in whole process of building of airtightness. Carefully and thoroughly conducted analysis provides information and recommendations for improving the quality and limitations of errors.