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Improving Indoor Environments with HVLS Fans
Distribution centers, manufacturing plants, and other large, open industrial facilities face a host of unique design and environmental control challenges. In the summer, they can become uncomfortably warm, while in winter their inhabitants often shiver at floor level while heated air rises into the rafters. They also face condensation-related issues, ventilation-related 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, savvy 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 employee comfort and health in all seasons, while providing additional benefits in buildings with no air conditioning. They also help to reduce energy consumption, combat air quality-related problems, and even can be integrated into fire prevention systems.
Seasonal Benefits of HVLS Fans
The environmental benefits of HVLS fans in both hot and cold weather have been well documented. In steamy climates, they can help industrial facilities guard against heat stroke, heat exhaustion, and other heat-related maladies by providing workers with an evaporative cooling sensation, reducing the effective temperature by 7-11 degrees. This not only makes employees safer and more productive, but also it allows for significantly lower settings on the air conditioning system.
HVLS fans' benefits are even more pronounced in the winter months. They mitigate the rising heat effect by destratifying layers of heated air, gently circulating warm air from the ceiling back toward employees at the floor level. Thus, facilities equipped with HVLS fans reduce the burden on their heating system and don't require as high a thermostat set-point to achieve a standard level of environmental comfort—reducing energy consumption and saving money.
Helping Fight Two Common Air Quality Issues
In addition to temperature moderation, HVLS fans are also helpful in combatting two common air-related health/safety issues: sweating slab syndrome and sick building syndrome.
Sweating slab syndrome (SSS) is a phenomenon that occurs when moisture intermittently develops on the surface of an interior concrete slab, such as a warehouse floor. SSS can increase the slipperiness of the concrete surface and pose a serious risk to the safety of workers and materials handling operations. Dew point condensation is a common cause of this moisture accumulation. This often happens in spring and summer when warm, humid air enters the structure through open doorways, windows, and vents. As that warm air diffuses throughout the structure, it will condense on any surface that is at or below dew point temperature—which is often the floor surface. When this balmy air enters, it takes far less time to change the interior air temperature than it does the temperature of the slab. With such a rapid change in conditions, the slab temperature can easily be found at or below dew point.
Many large facilities provide little air movement and may exhaust interior air through roof vents, creating negative pressure in the building. Negative pressure within a structure quickly allows exterior air and other conditions to enter the building when loading dock doors are open. HVLS ceiling fans can help reduce or eliminate slab sweating by minimizing ceiling-to-floor temperature differentials and increasing the surface evaporation rate. In addition, commercial dehumidification units can alter the interior building environment to help reduce or eliminate SSS.
Sick building syndrome (SBS) refers to situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, even though specific causes can’t be identified. In contrast, the term "building related illness" (BRI) is used when symptoms of diagnosable illness are identified and can be attributed directly to airborne building contaminants. Though the causes of SBS may be unknown, most affected employees have clinically identifiable symptoms (such as headache, dizziness, nausea), and they typically feel better soon after leaving the building.
There are a variety of causes for SBS, primarily related to stagnant or dead air. These include poor building design, maintenance, and/or operation of the structure's ventilation system. The ventilation system in particular is often found to be at the heart of the problem and can itself be a source of irritants. In addition, a poor ventilation system can result in a buildup of pollutants within the building, in which case the indoor environment can often have air quality much lower than the outdoor air. Humidity may also be a factor. While high relative humility may contribute to biological pollutant problems, an unusually low level may worsen the effects of mucosal irritants and may even prove irritating itself.
Although SSS and SBS have different causes, they have similar solutions, at least to some degree. Increasing ventilation rates and air distribution can often be a cost-effective means of reducing indoor pollutant levels and providing relief. HVAC systems should be designed to meet ventilation standards in local building codes, but many don't. Fortunately, HVLS fans can dramatically increase their effectiveness. For example, by minimizing ceiling-to-floor temperature differentials and increasing the surface evaporation rate, they help to reduce or eliminate slab sweating. For sick building syndrome, the increased air movement HVLS fans provide helps dissipate humidity and disperse concentrations of airborne contaminants, such as chemical fumes, pollens, bioaerosals, or other volatile organic compounds (VOCs).
Although high-speed ceiling or floor fans can also help increase air movement, HVLS fans move larger volumes of air while using less energy than high-speed fans and produce a less disruptive wind speed. In addition, having multiple floor fans can increase clutter and the chance of mishaps involving equipment and electrical cords. HVHS (High Volume, High Speed) fans can be used to complement HVLS fans in smaller areas or areas where direct "blasts" of air are needed for short periods of time.
Although HVLS fans impact up to 22,000 square feet of space, many large facilities employ multiple fans to enhance their environmental control. In facilities that have 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—creating a maintenance challenge. Fortunately, the most advanced HVLS fans can be linked into a network of up to 18 fans and run off 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, and cheese or wine storage. An optional ethernet port allows the system to be accessed via a remote device so they can be controlled via a smartphone or other mobile device. Additionally, they can be programmed into a Building Management System and connected to other infrastructure equipment such as exhaust fans. A "fire stop" option is also available, in which the BMS will automatically turn off the HVLS fans and activate sprinklers in the event of a fire.
A Healthy Decision . . . with Bottom-Line Impact
The use of HVLS fans has gained 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, warehouses, or ships. All can have a direct and significant impact on the organization's bottom line.
This article originally appeared in the March 2016 issue of Occupational Health & Safety.