J Burns wrote in :

I bought a 20" Lasco box fan because the store said it would move 2500
cfm for 80W. If it sounds too good to be true, it probably is.
According to my measurements, it moves about 1000 cfm for 91W.

Bigger fans move more air more efficiently. I don't know why there
don't seem to be inexpensive box fans bigger than 20".

The 30" Westinghouse 78108 ceiling fan is supposed to move 3900 cfm for
45W. It weighs 11 pounds and costs less than $50.

If I built a stand, could it be used to blow air out a window? Would
the motor bearings handle it? Would I need to build a wire cage?

Is there a better alternative?

I put my 20" box fan in the window, with the upper sash holding it in
place against the storm. Even with the window partially NOT filled by
the fan, it works fine. Gives me the option of reversing air flow even
with a non-reversible fan (turn it around). It's going upstairs that way
as I type.

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Best regards
Han
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