Here are some helpful tips in calculating the number of destratification fans needed for your space.

Calculating the number of fans to destratify a space

The calculations for destratification are driven by the cubic feet, or volume, of air within the area—not by the square footage! It doesn’t make any more sense to specify fans by square footage than it does to specify other HVAC or lighting on the basis on square footage alone.

To determine the number of ZOO fans required for a project requires doing a volumetric analysis. The design target that has proven to be effective in all but extreme conditions is one “air turn” per hour. Not “air exchange”—ZOO fans do not impact air balancing, nor do they add or subtract BTUs. What they do very effectively is to average the temperature and humidity within a given space. When hot and cold spots are eliminated, a space is more comfortable, and less expensive to heat or cool.

To determine the number of destratification fans required to turn the air over one time per hour, follow these steps:

First… Calculate Volume (all in feet or fractions of feet):

Length X Width X Average Ceiling Height = Volume (in cubic feet)

Second… Determine which ZOO Fan to use.

  • H-Series, for Open Ceilings and Free Hanging Installations, from 10’ to 100+’ high
  • IC-Series, for In-Ceiling and Drop Ceiling Installations, from 8’ to 50’ high

TIP: Every ZOO Fan is variable-speed controllable—individually, in zones, manually, automatically or via Building Automation. This allows for ease of installation and control across a broad range of applications.

Third… After selecting the fan size you are going to use, apply the following formula:

Volume of the space in cubic feet ÷ 60 (minutes in an hour) ÷ CFM (of the fan selected) =
The number of fans selected that are required to achieve one (1) air turn in one (1) hour.

Volume ÷ 60 ÷ CFM = The Number of Fans to Install

FOR EXAMPLE: A store with a 22.5′ ceiling that is 250′ wide and 175′ deep has the following volume.

175′ X 250′ X 22.5′ = 984,375 ft³

Use the H30 at 659 CFM:

984,375 ft³ ÷ 60 ÷ 659 = 24.9

Rounded up, the requirement is for (25) H30 Fans to turn the air in this space once per hour.

When you go to lay them out if you find that, due to the floor plan, specifying 24 or 26 fans makes more sense, then go that route—it will work, too.

Other Considerations:

There are instances where you should consider the next size up when selecting which fan to use. For example, in a 150,000-square foot warehouse with a ceiling height of 28’ where workers are active and a greater airflow is acceptable, consider the difference between the H30 and H60:

150,000 sq. ft. x 28 ft. = 4.2 million cubic feet

4,200,000 ÷ 60 = 70,000


70,000 ÷ 659 = 106 fans


70,000 ÷ 1171 = 60 fans

In a more constantly occupied space where your ceiling height is 30’ or less, and higher air speeds might cause discomfort for the occupants, it’s preferable to use the H30. Examples would be a grocery store or an auto dealer. This would create less draft and still destratify the space effectively. If your particular application is “on the margin,” call us up and tell us about the job—we’d be happy to help.

Placing the Fans

“Design is not just what it looks like and feels like. Design is how it works.” Steve Jobs

For the fans to be most effective, they should generally be evenly spaced throughout the facility and have a “clear shot” to the floor. As with any other equipment installation, the individual characteristics of the site will dictate overall fan layout, as well as the placement of each individual fan.

ZOO Fans are extremely versatile and can be installed as close as 12” to side-walls and ceilings. It is also easy to angle the fans to direct the airflow to hit or miss a particular area. The fans can be hung from the Gripples provided—please take a few minutes to read through the installation instructions to see the basic installation—or they can easily be hung from 3/8” all-thread down rod and a beam clamp—the preferred approach where the plan is to angle them.

Given the many different applications for ZOO Fans, you’ll no-doubt encounter situations that raise additional questions. Simply give us a call – we welcome the opportunity to talk to you!

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