Before there was air conditioning or mechanical ventilation, there was natural ventilation. We have come full circle in the quest for low energy and zero energy buildings. Natural ventilation is used on many projects, but how is it used and how effective is it? ASHRAE Standard 55 describes how natural ventilation can be assessed to meet adaptive comfort criteria, how comfortable is this criteria? The work presented shows natural ventilation applications in various locations around the world and the compliance or noncompliance to adaptive comfort criteria. The presentation also highlights areas where natural ventilation applications need to be strengthened.