Is a reflective barrier with perforations advisable for use laying over the top of other attic insulation as an upgrade?
That’s a big question with lots of “ifs.” If you can’t install the radiant barrier on the roof rafters it is ok to place on the floor. If there are AC ducts in the attic, they must be covered with the radiant barrier. If there are electrical wires running over the floor, you’ll need to be careful to ensure they are protected from the radiant barrier. If there is a lot of dust in your area that gets into the attic, you’ll need to monitor to make sure the dust doesn’t cover the surface of the radiant barrier, thereby reducing its effectiveness. And, last it is necessary that the radiant barrier is perforated to prevent moisture from building up in the mass under it.