moisture on my garage ceiling
If you run the engines of the cars in your garage then that is probably source of the high humidity and the moisture. If this is the case, then you need to vent that area when the engines are running and for a short time after the engines are shut off. Burning fuels create a lot of water vapor. If it is not from the cars engines, Then i would check for water infiltration from the roof area. With all that insulation and the vapor barrier you have created a tight atmosphere in the garage. Any operation in the garage that gives off moisture will allow that moisture to collect on the ceiling and walls which can allow for mold to grow.