Each fan would be 1500 cfm. I'm guessing the attic is about 3500 cubic feet.

I forgot to say this, but the current circuit, as far as I can tell, doesn't connect to the breaker box. The lines are dead and the attic ventilation fan hasn't worked since we bought the house. The fan doesn't spin smooth when manually rotated, so we assumed it needed replacing.

The handyman originally insisted on installing a 240 volt wiring and circuit breaker. I don't know much about electricity but that set off red flags. I have no problem going with higher gauge wiring if the cost is cents more, but there is no reason to run that many amps unless we're plan on charging an electric car in the attic.

Thank you for your comment.