How to Calculate Which Whole House Fan is Right for You
There are several things to keep in mind when trying to determine which type of whole house fan will work in your home, and you have to do your homework before you make a commitment.
If your house is well-insulated, multiply the square footage by 3. If your house lacks sufficient insulation, multiply the square footage by the ceiling height and then multiply the product of that by 0.5. The number you get from either of these calculations is an accurate estimate of the CFM number your fan will need to have. These numbers roughly range from 1 to 6 thousand.
One of the other things to keep in mind when choosing a fan is the shading of your home. If you are surrounded by a bunch of trees or other forms of shade, chances are your home gets less sun than average. This will keep it cooler than it otherwise would be.
The next thing to keep in mind is your roof. If it is made of a reflective material and is also a light color, this could also keep your home cooler than average.
Finally, these fans require that you already have adequate attic ventilation, and work best with two to four times the regular space of a roof vent.