By Andy Olson
Canada’s warehouses, manufacturing plants, and other large, open industrial facilities face unique environmental control challenges. During the country’s famously frigid winters, inhabitants often shiver at floor-level, while heated air rises into the rafters. However, in the summer, these spaces can become uncomfortably hot and sticky. They also face indoor air quality (IAQ) 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 employee comfort and health 365 days a year. They also help reduce energy consumption, combat IAQ concerns, and can even be integrated into fire prevention systems.
Spreading the warmth 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 specified areas of a building, they do not optimize airflow—and, as every grade-schooler knows, warm air rises. Thus, in tall warehouses there may be an 8 to 10 C (14 to 18 F) difference 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 setpoint, wasting precious energy and dollars (Figure 1).
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 metre or so 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 of difference from floor to 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 have 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 the ground level. Thus, in facilities with traditional high-speed ceiling fans, the full benefits of the HVAC system are rarely realized.
Heat stress protection
Much of urbanized Canada experiences hot and humid weather in the summer months—presenting problems for industrial facilities. Heat stroke, heat exhaustion, and other temperature-related medical issues can also directly affect an organization’s bottom line, causing insurance and regulatory headaches—not to mention lowering employee productivity and morale. With online commerce driving an ever-faster pace of shipping and receiving, and average monthly temperatures on the rise, it is more important than ever for facility managers to take precautions to guard against heat-related problems.
While adding air-conditioning to a plant or distribution centre is the best-case scenario, it is not always practical due to cost considerations and building configurations. With or without air-conditioning, most heat-stress-prone warehouses can benefit immensely from HVLS fans.
Although smaller, floor-mounted fans can be helpful in limited areas, their high-wind speed can cause problems while their noisy operation introduces other stress-inducing factors. They also use a relatively high amount of electricity. HVLS fans, on the other hand, use relatively little energy and provide a gentle, quiet breeze that is very comforting to workers. Various studies have estimated a 3.2 to 4.8-km/h (1.9 to 2.9-mph) air speed creates a cooling sensation of up to 6 C (10 F). Air moving faster than 8 km/h (5 mph) can be disruptive and provides little, if any, added cooling benefit.
The advantage of HVLS fans is their ability to move large volumes of air and create a steady, light breeze. When the breeze reaches people during the warm months, it creates an evaporative cooling effect and reduces the effective temperature by 5 to 6 C (9 to 10 F). To put this in perspective, the effective temperature of a 29-C (84-C) warehouse environment can be dropped to 23-C (73-C) by adding a fan moving air at 5 km/h (3 mph). (For more information, see NASA’s CR-1205-1 report). This 6-C (11-F) cooling sensation can make workers up to 35 per cent more productive.
Technically advanced HVLS fans can move large volumes of air over an area up to 2044 m2 (22,000 sf). A single HVLS fan can replace as many as 10 to 20 floor fans, reducing clutter on the ground and lowering the chances of an accident. By mixing air, HVLS fans also help air-conditioning systems work more efficiently, allowing them to be operated at a lower setpoint. The breeze from an HVLS fan typically allows up to a 2 to 3 C (3 to 5 F) increase in the air-conditioning system’s thermostat setting without affecting employee comfort.
