Following are some of the benefits of HVLS fans for heating:

• More effective and energy efficient than the high-speed fans that are typically used to draw warm air down from high-mounted heaters.

• Thermostats are effectively lowered and heating costs reduced. According to the U.S. Department of Energy, for each degree the thermostat setting can be lowered, a three percent reduction in fuel consumption can be achieved (http://www.eia.doe.gov/emeu/consumptionbriefs/recs/thermostat_settings/thermostat.html).

• Virtually eliminates the pool of overheated air above the heaters, thus reducing heat loss through roof vents and skylights and increasing heater efficiency.

• Provides adequate ventilation while requiring less heated air to be replaced with cold air from outside.

• Mixes air to eliminate hot and cold spots on the floor as well as overall stratification - especially important in buildings where people are working at different elevations.

• Quiet and non-disruptive operation.

• In new construction, the cost of HVLS commercial fans may be completely offset by elimination of ducting, HVAC tonnage, and auxiliary system fans.

Ventilation

Due to the Coanda effect, which is the tendency of a fluid jet to be attracted to a nearby surface (in physics, air is considered a fluid), fresh air tends to travel from the inlet opening (door, window or vent) to the exhaust fan along the path of least resistance, typically up the wall, across the ceiling, and out through the fan. This means that most of the air that is exhausted from the building is the fresh air that has just been drawn in instead of the stale air that was supposed to be exhausted. Since HVLS fans continually mix the air in a space, stale air gets mixed with the incoming fresh air and exhausted, so less incoming air is required to produce the correct number of air exchanges in any given building.

This reduced volume requirement:

• Reduces the number of high-speed exhaust fans needed, in some cases eliminating them altogether, cutting exhaust fan power consumption accordingly. (ASHRAE Standard 62)

•Reduces the loss of heated or cooled air since less "virgin" air must be drawn in from outside - thus reducing heating or air-conditioning costs.

FAN DESIGN

Compared with helicopters and airplanes, ceiling fans arouse little curiosity as to what makes them work. Yet they follow the same complex principles of aerodynamics and must be constructed in such a way that they are both efficient and do not negatively interfere with other environmental fields. As Jeff Johnson, Applications Engineer at MacroAir Technologies and former race car builder, says, "When I took a job to work on fans, I thought it would be boring. But between air and electricity and electronics they have come up with real surprises. There's a lot more going on than meets the eye. You'd think something as basic as a fan would be simple, but it's the devil in the details." CFM rating, airfoil blade design, EMI compliancy, and solidity ratios are some of those details. Design professionals should be acquainted with them when evaluating HVLS fans.