HVLS or overhead ceiling fans are an extremely efficient way of moving large quantities of air around large spaces, like warehouses, auditoriums, and even a hotel atriums. They can be big enough to produce a slight breeze, keeping sizable open spaces relatively cool by increasing the rate of evaporation off people’s skin.
HVLS stands for high volume, low speed. HVLS fans come in far larger sizes than regular ceiling fans, generally ranging from 8 feet to 24 feet in diameter. The blades rotate slower than a regular fan, too: usually from 60-200 rpm.
Because the blades of HVLS fans are so much larger than regular ceiling fans, they don’t need to move as fast as a smaller unit. Since the blades are longer, they push more air. In an ideal situation, the fan pushes a large quantity of air downwards towards the floor where it is distributed outward towards the walls. The air moves horizontally away from the fan until it hits a wall, before traveling back up the wall and across the ceiling towards the fan again. This creates a continuous flow of air that provides a cooling effect for occupants in the building. It’s a process called evaporative cooling, which cools a person’s body without the added cost of air conditioning. You can read about the differences, benefits, and drawbacks of both fans and air conditioning here.
Evaporative cooling is a process in which a person’s body feels cooler when air flows over their skin. Instead of cooling the temperature of the air in the room, the air movement from a fan increases the rate of evaporation of moisture like sweat. As this moisture evaporates, it carries heat away from your body making you feel cooler even though the room temperature hasn’t changed.
HVLS fans don’t just increase the rate of evaporation to provide a cooling effect in the summer; they can distribute warm air more evenly in the winter. When a large space is being heated in the winter, the warm air will rise to the ceiling, leaving the colder air near the floor. HVLS fans push the warmer rising air back down, where it mixes with the colder air. This produces a more evenly distributed temperature throughout large indoor spaces, like warehouses, auditoriums, convention centers, and gymnasiums.
Because of the larger surface area of the fan propellers, HVLS fans can increase energy efficiency. The blades of the fan move more air than regular ceiling fans, but they do so without drawing more power to increase the speed of rotation. This is a boon for larger spaces, since they don’t require the use of extra energy to generate good airflow and evenly distributed temperature.
There are two types of HVLS fans: direct drive and gear-driven. The gearless direct drive fan is quieter than its counterpart, and it requires less maintenance. It is a great choice for every building application. However, the direct drive overhead fan really shines in showrooms, convention centers, or other spaces where a quiet operation is necessary. Other benefits include less maintenance than a gear-driven motor, since they have fewer moving parts, and increased energy savings.
Gear-driven HVLS fans, on the other hand, use gears to assist the motor. The motor is a regular high RPM motor paired with a gearing system. This old-fashioned technology reduces motor speed and in turn, the speed of the fan. The many moving parts of the gear-driven motor results in higher energy costs and requires more maintenance than a direct drive fan, leading to potential downtime.
Another added benefit of an HVLS fan is that it can help control humidity and improve indoor air quality. Excess moisture in a building can promote the growth of harmful bacteria and mold. Since HVLS fans keep the air constantly moving, condensation buildup on surfaces like floors, walls, or windows is minimized and the risk of microorganism growth is reduced. By combining an HVAC unit with an HVLS fan, fresh supply air can also circulate over a much larger area to improve indoor air quality in the building. Similarly, when an exhaust fan is removing contaminated air from a building, the fan will draw from a somewhat localized area around itself, leaving pockets of stagnant, contaminated air in other parts of the building. By adding an HVLS fan, contaminated air from those stagnant areas can be “pushed” to the edges of the building so that the exhaust fan can extract this air from the space.
There are a few factors to consider when deciding which HVLS fan best suits your needs. Determining the correct model depends on a few things, the most important of which are:
The size of the fan
The size of the HVLS fan you choose has the most direct impact on the airflow in a space. The smallest option, generally 8 – 10 feet, are ideal for a smaller business, offices, restaurants, or upscale homes with large rooms, for example. The next step up is 12 - 16 feet. These mid-size fans can create comfortable air movement in gyms and fitness centers, school cafeterias, automotive garages, and more. HVLS fans measuring from 18-24 feet are used in very large indoor spaces, like sporting arenas, warehouses, aircraft hangars, manufacturing facilities, and distribution centers.
The number of fans
It’s likely that more than one fan might be required for larger spaces. In spaces with separate rooms, columns, or other air-blocking features, it may be necessary to install multiple fans.
Fan placement
Identifying proper placement of HVLS fans is a must before installation. HVLS fans should be installed in areas of the building that maximize airflow and avoid objects or equipment obstructing airflow. Depending on the building, you should determine how to avoid obstructions, including walls, storage racks, water pipes, and overhead HVAC ducts, before installation. Fans must be located with enough clearance to walls, HVAC ducts and diffusers, and building features like plumbing and electrical conduit for the safe operation of the fan.
Climate
HVLS fans provide benefits in any climate. In the colder months an HVLS fan should run in reverse, mixing the stratified air (the layers of colder and hotter air that occur) more evenly. When using an HVLS fan to evenly distribute the warmer air and mix it with the cooler air, the slower moving, large fan props use energy more efficiently, which can reduce wasted energy and lower costs.
In facilities where moisture buildup is a concern, the continuous circulation of air that an HVLS fan provides can increase evaporation and prevent contaminants from building up. Standard ceiling fans, while effective in small spaces, do not substantially increase the overall airflow in large spaces. But HVLS fans can provide increased air circulation, occupant cooling, and humidity control.
No matter the size of your facility, there is an HVLS fan that will suit your needs. By keeping the people in the building comfortable, productivity will increase. The correct fan will lower energy costs and help manage humidity, saving on costly repair bills that might occur from condensation. They can promote safety by keeping the floors in a workplace dry, and since an expansive indoor facility can cost a fortune to ensure a comfortable temperature, HVLS fans are a smart option. You can learn more about overhead (HVLS) fans here. Overhead HVLS Fans