garage insulation

I know a guy who started with a basic all steel, enclosed carport/shed.
First he put a mostly horizontal grid of 2x2 and 2x4 wood inside, on 2 foot centers, attached to the steel with flat head screws.
Afterwards the reflectix sheeting, shelves, cabinets, work bench, overhead lighting, you name it, was attached to the wood with staples ,nails, lag type hardware.
I don't know at what cost.