I have a raised ranch. The garage is located under the master bedroom and another bedroom. The master bedroom is one of the coldest spots in the house in the winter. I'm going to add an additional layer of insulation in the attic, over the entire top floor of the house. However, I would also like to add some extra insulation on the garage's ceiling.
I was thinking of adding something like this:
Personally, I would add the two inch stuff, just to get increased R value. The only locations it appears that I could not add the insulation would be above the garage door openers and the tracks for the openers. I would have to cut the insulation around this.