Technically, an HVLS — high-volume, low-speed — fan is a ceiling fan greater than 7 feet (2.1 meters) in diameter. Unlike a small, high-velocity fan that creates small, turbulent air streams that quickly disperse, an HVLS fan relies on size, not speed, to move a significant amount of air. Originally designed for large spaces such as barns and factories, HVLS fans have evolved as technology has rapidly improved. They now are found in a wide variety of industrial, commercial and residential spaces, often working in conjunction with HVAC systems for energy savings. In fact, energy-efficient HVLS fans have quickly assumed a leading role in the green building movement.

The air from an HVLS fan moves toward the floor in a column that radiates in all directions, flowing horizontally until it reaches a wall — or airflow from another fan — at which point it turns upward and flows back toward the fan. This creates convection-like air currents that build as the fan continues to spin. The increased air circulation effectively removes hot, humid air and replaces it with drier air. The result is a silent, non-disruptive and even distribution of 3- to 5-mph breezes over large spaces, with a perceived cooling effect on occupants of up to approximately 10°F (6°C). During winter, HVLS fans effectively redistribute warm air trapped at the ceiling down to floor level.