| This report summarizes the state of the art on building air tightness by reviewing the
current and recent literature on both research and practice. The focus of this report is
on techniques to measure the tightness of the building envelope and on what has been
learned by doing so. This report reviews over 100 of the most important publications
relating to the topic. The report covered the fundamentals of air leakage including the
hydrodynamics of leaks, which has led to all of the measurement techniques currently
in use. The measurement techniques reviewed focus on the fan pressurization
technique and its derivates, but the report covers novel techniques as well. Air
tightness metrics allow data to be shared and compared and the basic air tightness
metrics are reviewed and discussed as well as a brief discussion on norms and
normalization. The bulk of the report discusses data which has been taken over the
last twenty years and what it can tell us about buildings of different types, locations
and properties. | 