My brother in law had a new home constructed approx. 2 years ago. This past summer he noticed that there were dark lines on all the walls (interior and exterior) where the studs are. It looks like shadows that go from floor to ceiling in every room. He has a cathedral ceiling in the LR/kitchen and standard ceiling elsewhere, an attic fan which he uses for summer ventilation, as well as A/C and standard attic vents. He put 2 coats of primer paint on all walls and then painted all walls a light beige. He inquired with Sherwin Williams to see if it could be the paint and they indicated that if the paint was the problem, the darkening would be everywhere. He had the builder come out, but he claims he has never seen anything like it and has no idea what to tell him. He offered no solutions or suggestions. Our only thought is that moisture settled into the studs (somehow) and is now staining through the drywall...but the builder doesn't think that could be the problem. Can you offer any words of advice or suggestions on what we can look at to determine what has caused this problem -or- advise if you think repainting with some type of moisture sealing paint would work? Your help is much appreciated!