Insulation, Radiant and Vapor Barriers - Attic over unheated garage

We've recently moved into a 25 yr old home (Central Indiana) that has an unheated 2 car garage. The attic space above is well ventilated, and has no insulation. The inside garage temperature has been cold enough to freeze water.

Would it be wise (worth the cost) to add insulation to this attic space? If so, then do I need to install insulation with a vapor barrier?

Thanks in advance for your help.

If the garage is attached to the house, I would look at the attic insulation in the house. If you have 8" or less there, then contact a contractor and have cellulose blown into both the house and the garage attics. This will give you the largest reduction on your heating and cooling bills, and will be the least expensive in terms of time AND money) way to achieve that reduction. Insulating just the garage attic, even doing it yourself, won't make a very significant difference in your utility bills. A vapor barrier in the garage isn't necessary.

If the garage is NOT attached to the house, I wouldn't worry about it.