When it comes to heating large spaces, most facility managers aren’t going to immediately think about fans.
Typically used as devices to cool down employees and lower the perceived air temperature, the right type of fan can actually warm things up in a large, cavernous facility.
As counter-intuitive as it may seem, fans – specifically high-volume, low-speed (HVLS) fans – are even more important for warehouse temperature management during the cold weather months than in summer.
HVAC systems do an efficient job of providing heated or cooled air to specified areas of a building, but they don’t optimize airflow – and, as every grade schooler knows, warm air rises.
Thus, in tall warehouses there may be a significant temperature difference between the floor-level workspace and the ceiling. By continually mixing air through a process called destratification, HVLS fans can mitigate this problem, helping provide facility managers to provide more comfortable working environments and even cut energy usage by up to 30%.
Destratification Spreads the Warmth
During the heating season, there is often more than a 20-degree F difference between the floor and ceiling at most manufacturing plants and warehouses as a result of warm, light air rising and cold, heavy air settling.
Typically, the air temperature will be one-half to 1 degree F warmer for every foot in height. 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.
The chart below illustrates this concept:
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 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 – if any – of that air reaches people working at the ground level. Thus, in facilities with traditional ceiling fans, the full benefits of the HVAC system are rarely realized on the floor.
Less Energy = More Savings
Because HVLS fans are efficient, their return on initial investment often ranges from six months to two years. Payback on an HVLS fan varies according to a number of application variables. As shown in Table 1, winter energy savings are substantial. Users can reduce their heating bills by 20 to 30% when using an HVLS fan to gently mix warm air from the ceiling with cooler air below.
Important Aspects to Contemplate
There are a number of factors to consider when deciding how and when to use HVLS fans. They include obstructions such as pallet racks, machinery and product staging; personnel work areas; and overall building layout, to name a few. Larger diameter fans will move air further down rack aisles and over obstructions. Smaller diameter fans can be most effective in specific work areas, or where installation space is limited.
Fan suppliers can help configure an array of fans, determining the number, size and locations that provide the maximum benefit for the investment. They can also offer turnkey installation where on-site resources are not available.
While the basic concept is similar across all HVLS fan manufacturers, fan design and performance are key factors to consider. There are significant differences between manufacturers, including the shape and number of blades, blade tilt, hub construction, blade-to-hub connection, and safety features.
The performance of different designs will vary in the uniformity of air movement directly below the fan, as well as the height and reach of air movement outward from the fan’s diameter.
Other important considerations include ease of installation, fan controls, local representative support, trial program availability, and warranties.
Valuable Investment for Any Season
With all the advantages possible with HVLS fans, it’s no surprise the category has gained increased attention as a practical and affordable solution to improve air movement and enhance environmental control.
Additionally, recent technical advancements make them an even more attractive investment, with some fans as large as 24 feet in diameter for maximum air circulation in expansive areas, as well as touchscreen control stations that can efficiently operate up to 18 HVLS fans at once.
These types of fans are now recognized as a valuable supplement to help facility designers and engineers to control energy costs and improve employee comfort and productivity.
Capitalizing on the advantages of HVLS fans requires careful analysis of each application, as well as each HVLS fan design.
The information herein is provided as a general reference regarding the use of the applicable product(s) in specific applications. This information is provided without warranty. It is your responsibility to ensure that you are using all mentioned products properly in your specific application and in accordance with all laws and regulations.
Dan Anderson is the Product Manager for Environmental Control Solutions at Rite-Hite Fans