Double Hung-
Sounds like the seal between the panes is leaking and letting in the
condensation. It leaves the white streaky mess. I have a 1970's sliding
glass door in my bedroom that has long had a seal leak. The streaks have now
covered the panes so well that its a kinda neat faux marble effect. Gives us
the privacy you know without having to close the curtain!
Deco Window Glaze