Keeping homes dry and warm is essential for an effective controlled environment.  Controlling air flow has been overlooked as a key aspect of achieving these goals.  Air flow affects indoor air quality, comfort, building durability, condensation, combustion safety, recurring mold, icicles and more.  We will explore these and other issues and show how uncontrolled air flow can be the common link among many problems in homes. Air sealing solutions will also be presented. While "homes have to breathe", we will discuss what that means in a practical sense rather than it being a justification for sloppy installations and poor assemblies.