Under your roofing material is a moisture barrier like tyvek. Your attic space must be able "breathe" or you will end up with condensation where the cool a|c air of living space meets hot humid air. That's what ridge vents, gable vents and mechanical fans are about.I am curious why you have your walls wrapped in Tyvek but nothing on your ceiling? The air in the attic is the same humidity, although possibly different temp, as the air outside.