I bought a high velocity floor fan with metal blades (model 9220). On the
fastest setting, the fan vibrates slightly, but it has rubber bushing between
the fan and the feet, so the vibration is isolated.

However if I wedge the fan in a window to use as an exhaust fan, the whole house
starts to rumble since the fan cage is touching the window frame.

Is it common for this type of fan to vibrate due to off balanced blades? I don't
see any counter balancing weights on the fan blades. I imagine they would look
like those on a car wheel. I also don't see any holes drilled on the blades
(another way to balance)

Is there a kit for balancing fan blades?

If fans blades are not balanced, I wonder about 40 inch fans or large. Wouldn't
they vibrate so much they break themselves down?