How Destratification Works

Big Ass Fans Reduce Temperature Stratification and Winter Heating Costs in Hangars

The addition of HVLS fans is a cost-effective method to reduce stratification in large, open spaces such as aviation hangars. The decreased temperature differential minimizes heat loss through the building envelope, reduces equipment run time, and reduces gas usage. This report summarizes findings of a test completed at a 15,000 square-foot hangar in Central Kentucky.

Hangars present a tremendous air destratification energy savings opportunity because many have large, open spaces with high ceilings and lower insulation values than other more commonly occupied spaces. Heating hangars to meet comfortable temperature requirements often consumes large amounts of energy and produces an excessive amount of emissions. Like many other areas of industry, airports in Central Kentucky are now seeking energy-efficient systems to comply with increasingly stringent regulations without sacrificing occupant thermal comfort, all in an effort to reduce operating costs and reduce carbon footprint. BACKGROUND:

Cross section through space showing temperature with heaters on and fan off (top) versus fan on (bottom).

PROJECT SCOPE: A 15,000 square foot hangar with a 40 foot peak and 20 foot eaves was used as a test facility to validate the use of HVLS fans as a practical method for reducing thermal air stratification and HVAC usage in large spaces. A 20’ Powerfoil X3.0 fan was placed in the center of the facility with the blades approximately 27 feet above the floor. The space temperature control (a thermostat on an interior wall) was set at 65 degrees Fahrenheit (F). Temperature and humidity loggers were used to monitor the temperature along the back wall at 5 feet, 15 feet, and 35 feet above the floor. The HVLS fan was operated on an alternating weekly schedule. When the fan was turned on, the speed was maintained at 25% of the maximum operating speed for 24 hours a day to provide continuous air mixing without inducing draft effects to the occupants below.

Table 1 shows the average daily temperature at the three measurement locations and the differences in observed temperatures at the 35 foot elevation compared to the 5 foot and 15 foot elevations respectively when the HVLS fan was not in use. Table 2 shows similar >Page 1 Page 2

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