HVLS fans: The modern spin

Myths abound about HVLS fan technology: It’s expensive, it’s heavy, it’s ineffective. The physics behind the technology isn’t complex; it’s just about air movement. How the air is moved is the real science.

By Rick Oleson, Big Ass Fans July 15, 2008

Since the electric fan was invented 126 years ago by Schuyler Skaats Wheeler , people have been able to rely on fans for relief from the summer heat. The early technology was simple: Rapidly spinning blades produced a high-velocity current of air. The air activated the body’s natural cooling system by facilitating the evaporation of perspiration from the skin’s surface. This phenomenon made the direct beneficiary of the airflow feel cooler and more comfortable than the air temperature would indicate. The industrious workers of the 1800s were surely grateful.

Choosing the right HVLS fan for you: Do’s and Don’ts

* DO ask for a free facility evaluation to see where fans should be placed for optimum functionality.

* DO ask for an ROI calculation to determine expected energy savings from installing HVLS fans.

* DON’T expect that all fans are made the same. Different models are available for specific applications. A sales engineer should be able to help users find the best fit for a particular application and budget. Be sure to get all the details before buying.

* DO consider all costs of the fan purchase. An initial lower fan price may come with expensive installation costs or higher ownership costs. Do your research.

Feature story: HVLS = Cool efficiency

For the most part, the science of air movement has not come very far since then. Most fans manufactured for personal and personnel comfort in the 21st century, available at the local big-box store or through industrial suppliers, operate using substantially the same principles as Wheeler’s first appliance.The one (really, really) big exception to this is the high-volume, low-speed fan.

HVLS fans

are ceiling-mounted and vertical in design, and they range in size from 6 to 24-feet in diameter. Patented, aerodynamically-designed airfoils and small, energy-efficient motors allow HVLS fans to move huge volumes of air (more than 360,000 cfm) very slowly (less than 60 rpm) over very large areas (up to 30,000 square feet). By comparison, according to industry test data, a 48-inch high-velocity box fan likely also uses a 1-hp motor, but it generates just 7% as much air volume as a standard model HVLS fan — and it has to move five times as fast as an HVLS fan to do it!By moving a lot of air very slowly, the HVLS fan creates quiet, less disruptive airflow and makes for highly energy-efficient fans.The gentle air flow created by HVLS technology is ideally suited to manufacturing and warehousing facilities. Workers feel cooler and happier about their working conditions; management can keep productivity and morale high, while minimizing energy costs.Although HVLS technology has been eagerly adopted by satisfied facility managers all over the world, some skepticism remains. Here are some answers to 10 common HVLS fan myths.

Myth #1: Step away from a fan and you lose its effect.HVLS fans use their immense size, not speed, to move large volumes of air over sizeable spaces. The slow moving airfoils generate a downward flowing column of air equal to the fan’s diameter that projects outward when it hits the floor. A single HVLS fan can cover up to 30,000 square feet.

Myth #2: A fan that big must be an energy hog.HVLS fans take advantage of aerodynamic principles to keep them running in the most efficient manner possible. Design features such as hollow aluminum blades and air-capturing winglets maximize air movement while only requiring a 1- or 2-hp motor.

Myth #3: A fan that big must weigh a ton.The weight of the fan depends upon its size and design. Many fans don’t require any extra ceiling support.

Myth #4: Fans are loud and disruptive, kicking up dust and stirring around papers.Air-conditioning systems are generally much, much noisier than HVLS fans. And while some dust and dirt may be tossed into the air when it’s first turned on, the environment stabilizes as the fans run, leaving only a refreshing breeze.

Myth #5: Fans just push hot air around.In hot weather, fans are operated at the upper range of speed to circulate the air within a facility. In cold weather, the fans run at slow speeds to push warmer air down to the floor without producing a wind chill.

Myth #6: Fans must be reversed in the winter.A forward/reverse switch on the control unit of many HVLS fans allows users to change direction of the fan. But consider this before reversing your fans for the winter:

Myth #7: I can get the same results with smaller fans.An average 3-foot industrial fan uses aproduces less noise while cooling more people.

Myth #8: Low-speed equals one speed.Many HVLS fans come standard with a variable frequency drive to control speed.

Myth #9: Customers report many unexpected benefits when using HVLS fans, including reduced condensation and mold issues, elimination of slippery floors and packaging that retains its integrity because of reduced humidity.

Myth #10: Sustainability isn’t cheap.Some the most significant benefits users of HVLS fans have realized have had measurable impact on their bottom line. These benefits have been realized in two major areas: improvements in employee productivity and energy savings.

In the summer months, still, stagnant air in hot working environments causes employees to work more slowly and to require more frequent breaks. In the winter, cold, damp work spaces also adversely impact worker output. In the summer, HVLS fans generate gentle breezes within the entire facility, cooling workers, improving air quality, and, most importantly, keeping people on the job. In the winter, destratifying, or thoroughly mixing, air in the facility means that air from heaters and operations does not become trapped at ceiling level, and cold spots on the floor are eliminated. This improves production by improving the work environment.

Facility energy savings with HVLS fans can be realized year round. In the winter, thermostats can be lowered because workers will be more comfortable at lower settings when the fans are operating. In some situations, certain heating equipment can be deactivated because the facility will stay warm enough without it. In air conditioned facilities, the cooling effect of the fans’ gentle air movement allows users to raise their thermostats without loss of worker comfort, and equipment not needed to achieve cooling via a “blower effect’ can be turned off (or, in the case of expensive duct work, eliminated from a building’s design). Year round, adjustments of the thermostat can achieve energy savings of 3-5% for each degree of change — a significant amount in these energy-conscious times.

By eliminating smaller, inefficient “personal” fans, and/or making HVLS fans an essential part of your building’s energy conservation program, users can save big on building energy costs. While saving your bottom line may be your main motivation, there clearly are many other benefits to using HVLS fans that will just make the work space a nicer place to be.