Old tar paper wood chips nails dust you name it.
The nails in my attic are dripping is this normal.
In your case a attic access hatch or doorway is leaking badly allowing quantities of water laden air to come in contact with your roofing nails.
This is why you see the frost.
A point often overlooked is that since it s winter the water freezes on the cold nails.
Some times here when the attic gets cold enough there will be enough moisture put into the attic that you will see ice on the nails and frost on the sheathing.
The nails that you see in your attic get as cold as the outdoor temperature.
But that rarely happens.
Exposed roofing nails in attic dripping post by tnaval fri dec 29 2017 8 29 pm besides a table saw and a chop saw i used for a couple hours and my body heat.
The air in the attic has water in it and it condenses on the cold metal.
Moisture accumulation is most significant when outside temperatures are very cold because air holds less moisture as the temperature decreases.
Tonight my wife and i thought we smelled smoke so we got to looking and eventually decided it was coming from a recessed light in the kitchen.
Those fans need to go out of the house for sure.