The air in the attic has water in it and it condenses on the cold metal.
Frozen condensation in attic.
The warm moist air trapped inside of your home is coming into contact with the cold wooden surfaces in your attic forming large damaging water droplets.
This is why you see the frost.
Moisture forming on the glass window panes or other flat surfaces.
If there is a condensate trap insulate it or just remove it since it probably just runs outside from an attic space.
A point often overlooked is that since it s winter the water freezes on the cold nails.
Signs of condensation in the attic may include the following.
Well just like any drain line the water should exit the drain and there should be no concern about freezing.
Traces where water has trickled down the walls.
Sagging ridgeline drooping ceilings water leaks on interior walls and ceilings jammed doors cracked interior walls near the center of your home creaking sounds.
A tool like this shoots nails through shingles.
Condensation forms on the outside of the glass where the cold glass is coming into contact with the warm humid air.
The same thing may be happening on the inside of your attic.