I've been given conflicting information about the capabilities of radiant barrier paint. One paint company said it only works on the inside of a wall exposed to direct sunlight on the outside (i.e. the underside of a roof). Another guy said it reduces heat transfer through walls in general, even if neither is exposed to direct sunlight. My bathroom sits on top of my garage and is the hootest room in the house. Would painting the garage ceiling(drywall)with interior radiant barrier paint reduce the amount of heat rising through the floor of my bathroom?