Rafter mounted whole house fans are the most quiet of all because you cannot see them and you barely hear them.
Here is the latest list in order of performance to tests run per HVI-916: (This shows only fans that use EC motors – VentCool offers a higher flow but with a PSC motor which takes more power)
For 2019 Tamarack is one of the leaders in performance based on the Airscape design with 24 inch blades. They use a higher performance blade that helps their Model 5800 pull 5800 CFM. They also sell their older rafter mounted models, the 1100 CFM and 2200 models. All the rest are mounted on the ceiling.
For 2019 Thorwaldson is supplying the same performance as Tamarack using the proven 24 inch diameter shell. But in addition Thorwaldson eliminates the speed control that Airscape supplies because it does not show what speed is selected out of the 10 speeds available. Instead, you get a dial like a light dimmer so the position of the pointer indicates the speed. In 2017 Thorwaldson introduced the first high performance rooftop mounted whole house fan. It is perfect for homes with no attics like those on mid century modern homes and the adobe houses in New Mexico. Thorwaldson systems all work with the X10 and Insteon PC and smart phone remote control for AC power.
VentCool has released 3 lines of whole house fans, the Tahoe Series,the Summit Series and the Vista Series.
Tahoe uses PSC motors apparently to enable lowest cost compared to the use of EC motors. The Summit has the modern EC motor and a gravity damper. The Vista adds a motorized damper which is a nice touch but they are not worth the extra money.
For 2018 AirScape created a new and very attractive web site showing 2 product lines – Sierra and Ventura. The highest performance AirScape whole house fan is their Sierra 5300 that is rated at 5202 CFM and takes 825 watts to do that. It has 10 speeds and comes with a motorized damper at a price of $1929. The Ventura line comes with gravity dampers so the Ventura 5300 is a reasonably priced $1499 and it, too, pulls 5202 CFM.
AirScape announced their solution for homes without attics – their DVS or Direct Vent System. It is their 5300 mounted in a chassis ready for wall mounting. At $2,349.00 it is the highest price for air flow on the market at 44 cents per CFM. For comparison note that the Thorwaldson ER-8000 rooftop whole house fan is just 28 cents per CFM.
QuietCool announced a new line for 2018 but since the California Energy Commission forced them to post true CFM based on the HVI-916 test procedure, their performance is no longer as high as it was said to be. The ES is their “EnergySaver” line that uses the new ECM brushless DC motors. Their highest performance fan is their ES-7000 with 5170 CFM at 720 watts or just over 7 CFM/watt.
This company offers fans with motors from Germany that they would hope you favor over American made fans. But the performance is not there. Their most powerful fan , the 4.0, is rated at 4028 CFM and takes 640 watts to do that.
This company opened in 2018 to offer the strongest fan body on the market – made from spun aluminum with a stiffening ridge. Their most powerful fan , the QA-4800, is rated at 3396 CFM and takes 630 watts to do that. (5.4 CFM/Watt)
I need to mention the Superfan. This fan pulls 1850 CFM fan with (4) 8 inch inputs from 4 ducts. This low air flow system is not competitive with the systems shown above. It is sold by various outlets but it has been impossible so far to find the manufacturer.