A prior article described what a whole house fan is, and how it works.
This article explains how to size a whole house fan for your home.
Basically, you want the fan to exchange all the air in your home in twenty minutes or less.
The fans are rated in cubic feet per minute (CFM), but most (maybe all) whole house fans move less air than that which they are rated for.
About fifteen percent less.
First you calculate the cubic feet of your home.
This is the square footage of your living space times the height of your ceilings.
If you have a ,2800 square foot house with eight foot ceilings, your home is 22,400 cubic feet.
In order the fully exchange the air in twenty minutes, the calculation is 22,400 cubit feet divided by twenty minutes, which equals 1,120 cubic feet per minute.
Add fifteen percent to account for the inefficiency inherent in all electro mechanical devices, and you need a fan of at least 1,288 CFM.
The next size up is 1,700 CFM, which is what you would need.
We recommend installing a timer switch for your whole house fan so when you turn it on, you turn it on for a specified duration (20 minutes or so) so once the air in your home is fully exchanged, it simply turns off and you’re good until tomorrow.
This article is part of a series on how to cool your home without air conditioning.
And speaking of a whole house fan for your home ….. we would love to install one for you when you live in or near San Jose.