The paper deals with the indoor air quality in term or ever-increasing airtightness of building envelopes. In accordance with sustainable development, contemporary construction of buildings is focused on energy-efficient and green architecture. The main principle of the solution of these buildings is to achieve energy savings and reducing the production of greenhouse gas emissions. Cracks and gaps in the building envelope are places of uncontrolled air leakage. An uncontrolled escape air through building envelope contributes to the higher heat losses of the building. Energy-efficient buildings are characterized by high airtightness of the building envelope. Inadequate air change rate (1/h) may have significant impact on the indoor air quality. Ensuring fresh clean air together with temperature, relative humidity are key factors creating healthy indoor environments. Otherwise, there is an accumulation of concentrations of pollutants (volatile organic compounds) or microbes with negative impact on occupant’s comfort and their health.