Well, I  just decided to explore the many fan blade designs out there so you can learn even more about all the choices. The minimum number I could find is three and that is most common on the smaller systems, 1500 CFM to about 3000. You will note that 3 is also the standard for almost all HVAC condenser fans in homes. 3 blades are very efficient and, of course, least expensive compared to more blades.

As I have said elsewhere, Triangle Engineering makes the best hall ceiling mounted whole house fans and they standardized on 4 blades for nearly all their systems from 24 inches up to 48 inches.

Triangle 36 inch 4 blade










There are a few sources for 6 bladed fans. FanMan in Sacramento is one of the first to introduce 6 bladed fans as a unique way to set their products out from competition. They paid Triangle to tool up their special 6 bladed fan so Triangle will not sell it to anyone else in the US. It is interesting to note that Triangle is also the source for 6 bladed fans for Breezepower in Australia.

FanMan 36 6 blade by Triangle. Note the spring loaded motor ensures the belt tension is always like new












There are a few other sources for 6 bladed fans. One is, another is Both of these companies offer what they call the Zephyr blades. It appears that those companies buy their fans from a 3rd party, thought to be Air
Vent. Note that these models have bolted motors and the belt tension is not held constant by springs like the Triangle and Invisco models.

Air Vent 36 has bolted motor, no springs

Zephyr blade from Fresno. Note the vertical struts in back just like Air Vent

Zephyr from MyGreenHome. Note that the blade bolts and shape look exactly like the blade from Fresno

36 inch blade from Air Turbine, one of the best sources in the U.S. Note that the bolt pattern looks identical to the Zephyr















Invisco's 24 inch 6 blade fan. Invisco is using 6 blades or more on all their models.