Last years, interest in airtightness increases among all construction fields and airtightness becomes a major issue in the reduction of energy consumption in buildings. Nevertheless, there is a lack of understanding of air displacements through weak spots in buildings (airpaths). Firstly we develop first the concept of Potential Improvement Graph (PIG chart). These graphs represent the “improvement curves” of a given airpath (airflow indicator against airpath parameter). As an airpath can have multiple significant parameters, PIG charts can be n-dimension graphs. Such curves could be used by the contractor to anticipate the impact of a corrective measure on the airflow. Secondly we define three types of airpaths: opening, junction and residual. We suggest that a discontinuity in the air barrier can always be defined as a function of these three types of airpaths. This paper concludes on opportunities given by this work. (1) It could be used as a basis for other projects on air leakage at airpath scale. Such projects would force the researcher, and help the reader, to understand issues of air displacements. (2) This work can also be used as a basis for the development of tools to help field actors to deal with airtightness. Such tools would encourage their users to think in terms of air displacement.