In the past, an old concern was that a building could be "too tight".  This was based upon the concept of letting air leakage provide ventilation for indoor air pollutants.  Because air leakage can vary with the weather (wind and temperature) and is not uniform through out the whole house, this is no longer an acceptable practice.

Building science uses ASHRAE ventilation standards to develop a Building Airflow Standard (BAS).  This is used as a guide with blower door monitoring as work progresses, for both the homeowner and air sealing technicians to observe.