" Solar Flare" wrote in message
...
and mold... and sinus infections...and...


High humidity *could* be the OP's problem and that would lead to some other
issues.

But high humidity alone would *not* lead to *FROST* on the inside of the
window as the OP has. That can only happen if the inside surface of the
window/frame is really cold (32F). With a really cold frame, even 30% RH
inside will condense/frost on the window (dew point for 70F and 30RH is
about 37F).

Adding storm windows will help to reduce heat loss and stop the inside
frame/glass from getting so cold.

daestrom