On the North side of my house I have Andersen bay windows that tend to get
mildewy from the humidity and lack of direct sun. I have the house washed
every year including windows but I've notice that the mold stains are
visible from inside the house. In other words, the Andersen windows are
white vinyl clad, and mold is underneath the outside vinyl where it overlaps
the glass so it is visible from the inside of the house when you look thru
the window. But there is no way of touching that vinyl since that surface
is against the glass. Any suggestions on cleaning it?

I can't say that I am a fan of Andersen vinyl clad windows. On the north
side of the house they get moldy. On the south the sun had yellowed the
vinyl and made the vinyl almost brittle. The house is only 9 years old.