When I insulated by shed shop and office walls, I began by laying in that aluminized radiant barrier. The insulation went on top of that. I was surpirsed when we did the garage that the radiant barrier reduced roofing temperatlure by about 35 degrees. It only has an R rating of 4, but turning the infrared heat away is worth the effort to lay it in. I bought 4 ft wide rolls and cut them to fit between the studs. I also installed them between the ceiling joists, whice were not evenly spaced. Put R13 paper backed glass in next, then a 2 inch thick foam cut to fit precisely between the ceiling joists and held in place by finish nails hammered into the joists. No other covering on the ceiling. Walls are covered with a mix of ply and one whole 24 ft wall is covered in 1/4 inch pegboard. Never bothered with drywall in the shop. Stays warm in winter, but takes an hour to heat up when really cold. Small room AC cools nicely during summer here in the desert. I never painted the shops, just installed a lot of LED lighting
The more I do, the less I accomplish.