Mini-split: Two-story houses and stratification

A common complaint from occupants of low or moderate cost two-story houses and apartments is that their upstairs floor is often uncomfortably warm in the summer, while their main floor is either comfortable or too cool.1 The source of this problem can usually be traced to the exclusive use of single-zone2 all-air HVAC systems, which are the most common type used in much of North America's housing.3 This article describes one practical energy-saving solution to this cooling-mode stratification problem in such an existing multistory residence.