Lower energy consumption and improve comfort with HVLS fans
July 15, 2016 - Retailers, commercial facilities, manufacturing plants and virtually any large, open industrial facilities face unique environmental control challenges. During cold winter months, their inhabitants often shiver at floor level while heated air rises into the rafters. Conversely, balmy summer days can lead to a lot of uncomfortably hot and sticky people.
July 15, 2016 By Andy Olson
These types of facilities also face air quality issues, and—because of their sheer size—potential difficulties with zone-specific management.
While HVAC and building management systems (BMS) can address these problems to some extent, facilities managers now have another weapon in their arsenal: networked systems of high-volume, low-speed (HVLS) fans. By mixing heat-stratified layers of air, HVLS fans make HVAC systems more efficient, significantly improving the comfort and health of facility occupants/visitors all year long. They also help reduce energy consumption, combat air quality issues and can even be integrated into fire prevention systems.
Keeping cool with HVLS
Summer months can create a bevy of heat-related health concerns for a facility’s patrons and employees. Heat and exhaustion, and other temperature-related medical issues can directly affect an organization’s bottom line, creating insurance and regulatory headaches—not to mention lowering employee productivity and morale.
While adding air-conditioning is the best-case scenario, it isn’t always practical due to cost considerations and building configurations. With or without A/C, though, most heat stress-prone buildings can benefit immensely from HVLS fans.
Although smaller, floor-mounted fans can be helpful in limited areas, they guzzle energy and their high wind speed can cause problems. Plus, their noisy operating level introduces another stress-inducing factor. HVLS fans, on the other hand, use relatively little energy and provide a gentle, quiet breeze.
A 2-3 mph air speed creates a cooling sensation of 7-11 degrees F. To put this into perspective, the effective temperature of an 84 F environment can be dropped to 73 F by adding a fan moving air at 3 mph. Meantime, air moving faster than 5 mph can be disruptive and provides little, if any, added cooling benefit.
Technically advanced HVLS fans can move large volumes of air over an area up to 22,000 sf, replacing as many as 10 to 20 floor fans, which reduces clutter on the ground and lowers the chances of a mishap. By mixing air, HVLS fans also help A/C systems work more efficiently, allowing them to operate at a lower set point.
Saving energy in winter
While most people equate fan usage with warm summer weather, their benefits in winter may be even more pronounced. Although HVAC systems do an efficient job of providing heated or cooled air to specific areas of a building, they don’t optimize airflow; and, as every grade-schooler knows, warm air rises.
Thus, there may be a 20 F difference in high warehouses between the floor-level workspace and the ceiling during the heating season as a result of warm, light air rising and cold, heavy air settling. As such, a heating system must work hard for extended periods to maintain the temperature near the floor (or at the thermostat set point), wasting precious energy and dollars.
HVLS ceiling fans mitigate the rising heat effect by gently moving the warm air near the ceiling back down toward the floor where it is needed. The air reaches the floor below the fan where it then moves horizontally a few feet above the floor. The air eventually rises to the ceiling where it is cycled downward again. This mixing effect, known as destratification, creates a much more uniform air temperature with perhaps a single degree difference between the floor and ceiling. Facilities equipped with HVLS fans lower the burden on the heating system, reduce energy consumption and save money.
Conventional high-speed ceiling fans do not boast this effect. Although they have been used to help circulate air for many years, they are ineffective in moving the warm air from ceiling to floor. By quickly spreading airflow away from the fan, little of that air reaches people working at ground level. Thus, in facilities with traditional ceiling fans, the full benefits of the HVAC system are rarely realized.
Integrating HVLS with BMS
Although a single HVLS fan can cover an area of up to 22,000 sf, many large facilities employ multiple fans to enhance their environmental control. In facilities with ambient sunlight or temperature-affecting operations (such as loading docks) in one part of the building but not another, the fan speed, timing and other settings may need to vary by location, which creates a maintenance challenge.
Fortunately, advanced HVLS fans can be linked into networks of up to 18 fans and run off of a single controller. That controller allows for independent speed adjustments, scheduled start/stop times and the ability to start/stop based on preset temperature settings—a feature that can be very important in operations such as medicine, produce, cheese or wine storage.
An optional ethernet port allows the system to be accessed remotely so they can be controlled via a smartphone or other mobile device. Additionally, they can be programmed into a BMS and connected to other infrastructure equipment, such as exhaust fans. A fire stop option may also be available; in this case, the BMS will automatically turn off the HVLS fans and activate sprinklers in the event of a fire.
Improving comfort while reducing energy use
The use of HVLS fans is gaining increased attention as a practical and affordable solution to improving air movement, reducing heat stress and creating overall better environmental control. These types of fans are now recognized as a valuable supplement to help facility designers and engineers control energy costs and improve employee comfort and productivity. However, capitalizing on the advantages of HVLS fans does require careful analysis of each application, as well as each HVLS fan design.
Creating a more comfortable, healthier workplace clearly signals that a company’s management is willing to invest in employees and is serious about their safety, as well as the integrity of the products it manufactures handles. All can have a direct and significant impact on the organization’s bottom line.
Andy Olson is with Rite-Hite, a player in loading dock equipment, industrial doors, safety barriers, HVLS fans, industrial curtain walls, and more.
Types of heat stress
Heat stress can manifest in a variety of forms. While some are less severe than others, all are potentially dangerous. The mildest forms are heat fatigue, in which workers begin to lose concentration and perform erratically, and heat rash, which occurs when sweat ducts get plugged and skin becomes agitated and painful. People who’ve previously had heat rash or extreme sunburns can be more prone to this.
Heat stress may also cause heat cramps, typically in the larger muscles used during work, like back, arms, legs and abdomen. Dehydration and electrolyte imbalance caused by prolonged sweating are typically its causes.
Heat exhaustion, heat syncope (fainting) and heat stroke are among the most serious types of heat stress disorders. Heat syncope usually happens because of a pooling of blood in the lower extremities and dilated vessels of the skin, leading to low blood pressure and sudden unconsciousness.
Heat exhaustion can occur on its own or as a prelude to fainting. Common symptoms are similar to heat fatigue, but more severe including diarrhea, nausea and disorientation. Heat stroke is the most serious heat stress disorder and can be life-threatening. It occurs when the body’s systems of temperature regulation fail and body temperatures rise to critical levels. It can be marked by an absence of sweating, as well as confusion, fainting and/or convulsions. Hospitalization is a must for anyone who suffers a heat stroke.
Certain types of people are more prone to heat stress than others, including the elderly, smaller people, and people who exceed standard weight by 15% or more. (Interestingly, men tend to do better than women in hot, dry heat, but women fare better in extreme humidity.)
In all cases, fitness is a benefit, while drug and alcohol abuse, high blood pressure and chronic heart problems or other chronic diseases are disadvantages. The pace of work is a factor across all categories as well, as the more energy any worker expends, the more at risk they are of a heat stress-related episode.
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