You made one very important statement: It seems to do this only when the house is warm inside and cold outside.
The house is leaking warm air into the cold attic. Warm air holds a LOT more moisture than cold air. When the warm air comes in 'contact' with a cold surface (your roofing nails), the moisture condenses out (onto the nails). You need to evaluate your insulation situation. Maybe it's missing in places, maybe it's got 'gaps' in it, maybe the bathroom ceiling (or other rooms below the attic) is leaking warm air into the attic via holes or cracks or whatever. It's ALSO possible that warm air is escaping the bathroom fan's housing or from the fan's ductwork too. Maybe if you run the fan and go into the attic, you can feel around the ductwork. The duct MUST be insulated! You can buy 1/2" duct insulation at the Home Center. Buy yourself some SILVER Duct Tape; not 'plain' duct tape. The folks in the Plumbing Aisle can help you w/this. You should also 'feel around' up in the attic above the bathroom when the fan is off as well. Be sure the attic door is closed off (as if you weren't up there.) If the door is open while you're up there, you won't have the same 'effect' when it's closed. Solicite the help of a friend if necessary.
Again, just because you may find some leaks in your ceiling above the bathroom and you fix those, and/or you insulate your ductwork, don't stop there. Keep an eye on the attic to see how well your efforts paid off. You might find leaks elsewhere. Remember NOT to compress the insulation that's up there.
My best to ya and hope this helps.
Jay J -Moderator
PS: Be careful when working w/insulation around electrical fixtures. Depending on the fixture, covering it up completely or in part MAY be a fire hazard. Be sure of the 'situation' before you do that ...
PPS: God Bless America!
[This message has been edited by Jay J (edited October 26, 2001).]
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