The current legislative standards require as much as possible energy efficient construction. Airtightness is a key component of energy-efficient buildings. Airtightness is characterized by air leakage through the building envelopes. Untightness leads to uncontrolled air exchange and increased heat loss. Using the exploratory analysis of variables is analyzed the state of the airtightness of energy-efficient buildings in the United Kingdoms in recent years. The source of data sample set on the airtightness of UK energy efficient buildings is Low Energy Building Database (LEB). The sample of the data set contains information about 81 energy efficient buildings of different occupation date, location, construction type and values of airtightness. The mean is represented by value 1.44 m3/(h.m2) at 50 Pa. The minimum value is 0.33 m3/(h.m2) and the maximum value is 4.59 m3/(h.m2) for this set of data. In a global perspective, the energy efficient buildings with high-quality airtight building envelopes represent a positive externality in terms of increasing the energy efficiency of the building sector and reducing the production of greenhouse gases with regards to sustainable development.