Size is very important to a whole house fan system. If a whole house fan system is not sized properly, meaning enough airflow, the system will not work effectively.
Airflow is measured in CFM, or Cubic Feet Per Minute. Here is the formula for proper sizing:
For a “good” system, 2 CFM per square foot of living space.
For a “better” system, 2.5 CFM per square foot of living space.
For the “best” system, 3 or more CFM per square foot of living space.
This math formula will work every time, for any size home, and as always the more airflow the better.
However, there are two other considerations that need to be taken into account when sizing a system.
The first consideration is the location. If the home is located in a coastal region where the climate is much cooler than a desert, for example, a “good” system will work great.
But in a desert climate, the best system would deliver the best results.
The second consideration is ceiling height. If the ceilings in the home are taller than 8 feet, be sure to size the system a little bit larger to account for the increased air volume inside of the home.
Remember, the sizing formulas are backed by the Department of Energy, PG&E, and the California Energy Commission.
If sized properly, the whole house fan system will result in a totally satisfied customer every time!