High Volume Low Speed Fans

For hundreds of years, people residing in warm weather areas have utilized the cooling abilities of slow-moving air. In British India, servants would manually propel overhead circling fans called punkas; large ceiling fans were used in pre-Civil War southern mansions. Southern mansions before the Civil War used large ceiling fans, and servants in British India would manually operate overhead fans called punkas. Fans quickly became motorized as electric motor technology improved. By speeding the fans up, engineers hoped to intensify the air displacement, and thus, increase the cooling power. However, any speed faster than a gentle breeze could be unpleasant, drafty, and even disruptive. Beyond four or five miles per hour, the air doesn't have much more of a cooling benefit. It may come as a surprise, but slow moving air cools and ventilates best in hot conditions of low humidity.

For a long time, cooling large spaces required multiple, smaller high-speed fans that individually weren't capable of enough coverage for a wide area. Relying on multiple high-speed fans like this meant dealing with maintenance concerns and high energy costs. That all changed in 1995, however, when Walter Boyd, an engineer and designer, developed High Volume Low Speed fans, or HVLS fans. HLVS warehouse ceiling fans quickly presented themselves as an efficient cooling alternative for large open spaces; places like commercial, agricultural, or industrial buildings.

Some designers, perhaps unsure with the exact technology behind HVLS fans may be more familiar, and even comfortable, with using only HVAC systems for heating and cooling. But HVLS fans are effective, and they are efficient, and they owe it to the amount of airflow the aerodynamic blades are able to generate. The total efficacy of a fan is determined by the amount of cubic feet of air per minute (CFM) a fan can produce.

HVLS fans are best apt for open spaces with large ceilings; at minimum, a height of 15 feet. Experts in mechanical efficiency have deemed HVLS fans to be the most energy efficient type of air-circulating fan. While HVLS fans use their size to increase air displacement, a traditional high speed requires increasing its speed to move more air. And according to physics principles, the power required to drive a fan is equivalent to the fan's speed cubed.

So 8 times the amount of power must be provided in order for a fan to double its speed; in the case of high speed fans, that means 8 times the amount of electrical power. Consider a high speed fan capable of delivering air at 20 mph; it will require 64 times the power as a fan delivering air at speeds of only 5 mph. The large size of the industrial shop fans make it possible to move sizable amounts of air at low speeds, without requiring the additional power or speed. Additionally, for warmer months in places without air conditioning, the slow-moving air created by an HVLS fan is more apt to break up the moisture-rich layer that can surround people, leading to a cooling evaporation.