How Important is CFM/CMH When Choosing an Evaporative Air Cooler

Who doesn’t like the feeling of a cool ocean breeze on their skin? With an evaporative air cooler (EAC), you can experience the same feeling every day in your own home. But before you go out and buy the first EAC that catches your eye, you should learn what CFM/CMH is and how it affects the performance of EACs.

How Do Evaporative Air Coolers Work?

EACs are surprisingly simple machines. They rely on the natural power of evaporation by pulling hot, dry air through a moistened pad. As the pad absorbs the heat from the air, the moisture in the pad evaporates, cooling the air by as much as 20 degrees.

Because most EACs only contain a simple water pump and a ventilator, they are cheap to operate, easy to maintain, and extremely reliable. Instead of recirculating the same air inside a building like traditional air conditioners, EACs continuously pull in fresh air from outside, cool it, and circulate it through your home while pushing stale air out through an open window or door.

What is CFM/CMH?

To choose the right size evaporative cooler for your home, it’s important to know how many cubic feet of air per minute (CFM) or cubic meters per hour (CMH) it can pump. It’s also useful to know the speed of air, which is expressed either in feet per second (FPS) or meters per second (MPS).

A research paper presented during the annual International Joint Conference on Materials Science and Engineering states that “the heat absorption rate is increased by higher velocity.” The researchers found the optimal speed of air to be exactly 3.4 MPS. This explains why some manufacturers of EACs are able to claim very high CFM/CMH values even though the actual performance of their products is sub-par because of insufficient airspeed.

How to Choose the Right Size EAC

Choosing the right size EAC for your home is relatively simple. The only thing you need to do is determine how many CFM/CMH you need:

  1. Determine the average ceiling height in your home.
  2. Multiply the square footage by the average ceiling height in your home.
  3. Divide the number you get by two to arrive at two air changes per minute.

For example: 2,000 sq. ft. x 8 ft. = 16,000 / 2 = 8,000 CFM

It’s important to remember that there are many other parameters besides CFM/CMH to take into consideration when choosing an EAC, including your local humidity level and extra features offered. EACs are packed with a variety of features: carbon dust filters that can trap allergens and odors, remote controls, special energy efficiency, drainage options, and more.

In the next section, we recommend four EACs, each offering a different cooling capacity and set of features. We recommend you determine how many CFM/CMH you need and then pick an EAC that meet your requirements and offers the most compelling features at the most attractive price.


Honeywell CO48PM

Perfect for the dry air of the US Southwest, the Honeywell CO48PM is a weather-resistant EAC, especially designed for outdoor use. It’s rated at 1062 CFM and has a 12.7-gallon tank, and it comes with a hose connection for continuous water supply as well as an ice compartment for extra-chilled air.


Honeywell CL30XCWW

The Honeywell CL30XCWW is a compact EAC with a cooling capacity of 525 CFM and cooling coverage of 320 sq. ft. It has an ice compartment, a detachable water tank, and a garden hose connection. You can operate it with a remote control that comes along with the unit.


Honeywell TC50PEU

This EAC can be used indoors and in covered outdoor areas. It's a sleek and compact unit that boasts a 12.5-gallon water tank and operates with 3 fan speeds. It comes with a remote control and dust filters that are easily washable. 

1 comment

I want to know more about the drainage will I have to dump water before I buy one

Joann West June 05, 2019
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