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Fan has louvers that close tightly when not in use. This effectively seals off the attic and gives complete control. Many days I do not use it at all, just like AC or Heater. It is a tool that owners learn how to best use.
If it is a cold wintery day, it is normally not used, but if the outdoors raised above house ambient in the afternoon then you can bring in some free, welcome, warmth.
A side benefit is that you can open a screened door or window near where you are sitting and feel a pleasent cooling breeze when the CC is running. This often is enough you will not need to turn on your AC to remain comfy.
It is kind of like opening and closing your blinds to take advantage of solar warming. Some will not feel it worth the bother, but if you are Eco or frugal, it is an easy way to avoid using the heater or AC.
Simply, it makes opening a window about 10X more effective. If you have great breezes and flow through your house, then the fan is probably not that necessary.
Usually guys are more active in optimizing it's use, expecially if they are the ones paying the bills.
The fans are quiet enough that they do not disturb sleeping. It is a pleasant soft sound that we do not find to be objectionable.
Quiet Cool has thousands of installers, expecially in areas where the climate is most conducive for their use. They are happy to visit your home and do an evaluation as to their effictiveness. They will check your attic for proper ventilation, and will notify you if additional (extra cost) vents would be required to make their systems effective.
They carry about 10 different sizes and configurations with 1, 2 or 3 speed controllers. They can be adjusted by convenient wall switch or even more convenient app. They cannot be turned on when away from your house, as someone needs to be sure a window is open for them to circulate air. If a window is not open, then the fan will tend to such air through any inlets like electrical sockets or chimneys.
It is kind of like the old days when you needed to crack a window in your car to make the heater work better. Modern cars are not so tightly sealed, so no longer necessary to crack a window. This is why it was often hard to slam shut the doors in VWs as they were so tightly sealed the air inside the car had no place to go and would compress.
For many climates they are super cost efficient, for others not so much.