Whole house fans are sized in cubic feet per minute (cfm) of cooling power.
To decide the size you will need, first compute the volume of your house in cubic feet. To do that, multiply the square footage of the floor area you want to cool by the height from floor to ceiling. Assume that volume and multiply by 30 to 60 air exchanges per hour (depending upon the ability you need). Then divide by 60 minutes to get the cubic feet per minute of capability your house necessitates. [(Square feet x room height) x 30 or 60/ 60 = cfm required.]
There are various kind of Whole House Fans which are
(1).Ceiling-mounted Whole House Fans: – A ceiling-mounted whole house fan is the biggest and most noisy of all. They come in two designs -
Direct Drive Fans: The fan blade on a direct drive fan are attached directly to the drive shaft and need less maintenance to keep the system operating.
Belt Drive Fans: A belt-driven whole house fan has a belt that connects the motor to the fan blades. This type of system requires more care, and belts must be exchanged when worn, in general every two years.
(2) Attic rafter mounted fans – these are the most quiet.