Few years back I looked in the attic and noticed that I'm getting
frost on the roof decking above the shower in my bathroom. Only
happens when its extremely cold out. Zero degrees. Obviously what's
happening is that moisture from the shower is rising, hitting the cold
decking and collecting. The frost than melts
and darkens the decking and trusses in this localized area above the
shower.

Originally, we were talking large patches of frost probably around
the
size of a standard shower stall. Heavy white. If you'd scratch it
you would get snow. Figured that this couldn't be good
so a couple years back hired a guy to take care of the problem. He
installed these heavy-duty bathroom fans to suck out the moisture
(and
all the heat too). In addition, he put in a new light can in the
shower stall that supposedly had a better seal. His theory had been
that the moisture had been seeping through the fixture.

Now I take a shower with the door to the bedroom open and we're
moving
the air so efficiently that the mirror fogs up at the top only and
even then it's not bad. This helped my frost problem in the attic a
little. Very little.

The next year he installed gable vents and soffits.

Then we painted the shower ceiling with this special vapor barrier
paint.

Then we installed ridge vents.

Today, Wisconsin was hit with frigid weather. Poked my head in
the attic to see how we were doing. Sure enough, a faint swatch a
foot by maybe two feet on the decking and a heavier one inch band
following the upper edge of a truss all the way down to the eaves.
This one is so white that you can not see the wood underneath.

Starting to get frustrated here. Anyone have any suggestions?

Thank you for your time,