The builder of my house neglected to place an exhaust fan in my guest bathroom. When I brought that to their attention, they replied that code only requires fans in bathrooms that don't have open-able windows. But the lack of one in my guest bath has always bugged me, so I'd like to add one.
But the bathroom is only "ganged" for the lightswitch that it presently needs. (And, the feeder from the circuit panel enters at that switch.) Would it be permissible to tie the exhaust fan into the switched side of that gang box, or am I required to give the fan a dedicated switch of its own?