Hi! I have a home that faces north- half the roof faces north and gets little direct sun, while the other half faces south and gets direct sun year round. For two winters now the north side has shown a problem. After cold, rainy weather in December when I go into the attic, one half of the north facing roof is wet. It appears to be condensation rather than leaks. A few nails protrude through into the attic and have fine droplets condensed on them. Oh, the roof lacks a layer of tar-paper- that is, it's just the shingles. Folks in my subdivision tell me that the houses were done that way (bad idea!) This is my third winter and I've only noticed this two years, both when the roof was cold. I suspect condensation. I suspect I need a membrane layer with singles over it. Any ideas?