Attic ventilation is intended to remove moisture from the area in the winter months and to remove solar heat during the summer months. Preventing moisture from entering the attic in the first place is now recognized as the best way to keep attic insulation dry.
While it is important to seal air gaps around your house, it is also important to make sure that your house is able to exchange air as well.
Ceilings and bypasses need to be sealed, and insulation brought to adequate levels. If kitchen and bath exhaust vents are not vented through the roof, they are venting warm, moist air into the attic. This adds to the problems of both mold and frost.
RSI adds insulated ducting to the exhaust fans and vents, then through the roof to a dampened roof fan.