When your home leaks air, infiltration literally sends energy-efficiency out the window, while one of the most serious results of water leakage is mold. 

Davidovic,Srebric,and Burnett of Pennsylvania State University write, "In North America, residential enclosure walls are often built with provision for natural convection and, therefore, provide potential for ventilation drying within the wall. At present, our knowledge of the drying process in the wall systems is limited. The drying process is driven by very low airflow rates with complex flow patterns through the narrow and irregular wall cavities, resulting mostly in unstable ventilation driven by natural convection." 

They continue, "Nevertheless, the convective drying process is probably one of the key mechanisms for mold suppression in residential walls in the US."