Our house is only 4 years old, has an open beam ceiling. We are starting to see the shadows of the wall and ceiling studs and the drywall screws through the paint. Is this mold or mildew? Are the drywall screws rusting? We have had problems with the roof vent and blowing snow getting into the opening. The ridge cap was removed and a foam strip (like weather stripping) was used to seal the air gap but still allow airflow. Do we need to add more ventilation in the roof or is it an inside moisture problem. I have checked the bathroom vents and ductwork they are sealed and vent outside. The house is weather tight, could wall vents help?