"pln" wrote in message
oups.com...

Thanks for the reply Al.

The vapor barrier is facing the second floor ceiling so that is ok.

The symptons are the nails do have fost on them when it's gets really
cold and there is some frost on the plywood sheating. The north side of
the roof does have some mositure right by the soffet vents (the
affected mositure area is a goes up 2 - 3 feet into the attic).

This sounds pretty normal for an attic in New England. Some moisture will
inevitably leak into the attic space or it can just be normal ambient
moisture from the outdoors. When it's really cold out, it will condense on
the nearest cold surface before it has a chance to get vented out. Consider
when your car gets frosted up on the outside of the windshield even when
there is no precipitation. It's just moisture in the air condensing on a
cold surface and there's unlimited venting around your car. That same
moisture will frost up the nail heads and the plywood sheathing even in a
well vented attic.

-al sung
Rapid Realm Technology, Inc.
Hopkinton, MA