Old buildings tended to "leak" air more that new ones. In the old days, we used to simply calls these leaks "drafts" but now we're hipper and call it air infiltration (or exfiltration) depending on which way the air is moving to the indoors (or toward the outdoors). This behavior, namely the absence of much airflow, is sometimes referred to as how "tight" a building is.
A tight wall has the advantage that less air moves through it and since moving air carries energy with it, a building with tight walls requires less energy to keep the indoor spaces at the proper temperature. This is not rocket science but a tight wall also allows less moisture to sneak in (or out) of a wall and hence can contribute, both good and bad, to condensation, retention of odors and other building performance issues. The recent expanded use of air and water barriers in exterior walls can increase the tightness of walls and some people feel this may be part of the cause with various types of moisture-related problems in newer construction.