*Does that much moisture actually travel through the
ceiling? *

The best way to explain it is that you have moist - warm - rising
air , penetrating the ceiling . It reaches the colder attic and is
condensating under the barrier . It may actually frost up under there
until it warms up . When it thaws , then the problem starts . Just
like a glass off ice water . Cold water inside the glass , warm on the
outside . Then the glass sweats and you have moisture on the outside .
More so if it is humid out . If this indeed is your problem , the
humidity in your kitchen as you cook could cause these problems . If
so , you need to rid your house of extra humidity possibly caused by
cooking or showers .

But then there is the damming problem ! The heat loss from your
house helps cause this . Just make sure you find the true culprit .