July 5, 2018

How Much CFM Does a Whole House Fan Use and Need?

traditional whole house fan

It would first be wise to discuss what exactly CFM is. Firstly, it is an acronym. The letters stand for cubic feet per minute.  It is a measurement of the velocity at which air flows into or out of a space. The CFM measurement often is used in reference to a computer’s cooling system.

Unscientifically, it is the amount of air the that needs to be pushed through a home to reach optimal coolness. Each whole house fan has their own CFM. Quiet Cool models in both lines range from 1500 CFM to 6400.

The Classic line uses standard efficiency PSC (or Permanent Split Capacitor) motor. This motor offers above average efficiency, especially when compared with the old shaded-pole motors used in many fans still on the market today. The Energy Saver line uses our high-efficiency ECM (or Electronically Commutated Motor) that offers the best energy-efficiency in the business.

Models in the Trident and Stealth pro also both line range between 1500 to 6500. The Trident Pro uses similar PSC motors as the Classic line and the Stealth Pro uses similar ECM motors as the Energy Saver lines.

All of these different models range around the same CFM and it is crucial that a home chooses a model that fits the amount of space it has. A larger home would need more while a smaller home could settle for 1500 worth.

Employees at Quiet Cool would be happy to inform a potential whole house buyer on how much they would need for their particular space but the general rule is for a “good” system, you want 2 CFM per square foot of living space, for a “better” system, you want 2.5 CFM per square foot of living space, and for the “best” system, you want 3 or more CFM per square foot of living space.

Some companies that sell whole house fans try to undersize homeowners, suggesting fans that are less than 1 CFM per square foot. This makes the fan much too weak while the price is more appetizing for customers. QuietCool’s sizing formula, meanwhile, is backed by the Department of Energy, PG&E, and the California Energy Commission.

CFM is crucial to any whole house fan and can make the product wildly better depending on the size of a home.


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