For the past 2 days, my wife has noticed a small wet spot on the inside of an outside wall. Curious that it might be coming from the attic, I went up (we have pull-down stairs) to check it out. NOTE: We live in Maryland where temps were in the teens last night. I noticed that ALL the nail tips from the roofing shingles were covered with thick frost, as were the side walls. I didn't want to have the hatch opened for too long, so I took a quick look around, but didn't see anything overtly dripping down the wall where the wet spot was. Is what I've described about the attic frost a normal condition? Can anyone help? Thank you. David

I have a 1955 brick & plaster ranch house with a large cold basement. Cold air comes into basement from the perimeter where the 1st floor and joists meet top of foundation. I want to insulate between the joists but I am concerned that insulation installed where the 1st floor meets the top of the foundation will trap vapor between 1st floor plaster walls and brick. Will sealing off the air that is coming into the basement from the perimeter cause a problem between the plaster walls on the first floor and the brick?