I want to insulate my garage ceiling. I'd like to staple​ this to joists and set bat insulation on top to give a better r-value. Will this work?

Yes it will. It will add more radiant factors than r value

Dear BinPA: No, Reflectix and similar 'reflective / radiant barrier' products will not be effective with your garage ceiling. Why? First, Reflectix provides only R-1 by itself; the claims on the package are based on a sealed air gap you must build / create on one side. Second: Reflectix and similar products are not effective in winter, because cold cannot be "reflected" and warmer air is not radiant. In short, standard insulation products from Lowes will be more effective, e.g. foam board and Roxul rock wool. Here are some recommendations: (a) Fill your joist bays with Roxul ComfortBatt, which is much denser than fiberglass and provides R-4 per inch. You can hold the batts in place with Simpson insulation wire. (b) Then install 1" sheets of foam board on the bottom of the joists. This will add R-5, and (equally important) allow you to create an effective air seal. Seal all of the joints and edges to block air leaks. DAP 230 works well for joints. The 'Window and Door' version of Great Stuff spray foam is good for larger gaps. (c) Then install 1/2" drywall over the foam board. Foam board is flammable, and MUST be covered by an approved 'thermal barrier' in any garage, living space, basement or attic storage area. The standard is 1/2" drywall. This will also give you a nice finished surface for your garage ceiling. I hope this is helpful. Mark