I think you will be pulling the kettle off the floor with that fan!
Seriously--just VENT the kettle to the atmosphere, you don't need a fan for exhausting the kettle unless your vertical run is over ~20 feet.
You could also condense the vapor stream with a simple water spray condenser. Route your Kettle stack to a drain right by the kettle. Plumb spray nozzles with 1/2 copper pipe into the stack. Use a ball valve to control the spray nozzle's flowrate. You neighbors will complain less about the smell, although there is a drawback of using more water in your brewery.