I live in a small house (900 square feet) with exhaust-only ventilation (80 cfs panosonic fan in the only bath).  The fan in question senses humidity and has a motion sensor switch.  I can set the humidity at which the fan turns on, and the motion sensor delay in minutes (if any).  I realize there may be more optimal set-ups for ventilation, but given my situation I’m looking for suggestions on where to set the fan.  The house is tight, with plaster walls inside and out, and air sealing at the sill and around all the electrical boxes, if that makes any difference.  I’m in 4C, Western Oregon.  The house is home to 2 adults and two young children.

Any ideas are appreciated!
thanks,
chris