Fantastic fans are very loud. I have a 31 ft MH and they drove me nuts with the noise they make I couldn't fathom it in a small Class B.
I ripped out the fantastic fans and installed one MaxxAir turbo fan on my RV.
The fan is on the OUTSIDE of the RV. You don't even hear it and IMHO they work far better recycling the air. 3 fan speeds and Thermostat controls. Power is unbelievable, the silence inside the MH priceless.
Since I put these on I rarely have to use the air conditioning. And it's also priceless for me while driving down the road to keep the coach cool for the dogs just with the fan.
Put one of these on you won't regret it! :C