Recently I had some rotting trim replaced on the exterior of a bathroom window. It's an east facing window (in N. California) and does show signs of humidity on the inside in the mornings. But... only the lower exterior corners showed signs of rot. The exterior vent holes were clean and open. The question is 'what caused the rot' and 'now that it's been repaired should I caulk the circumference of the new trim?'
The exterior of the house is Wyerhauser style siding. But that's an entirely different story.