I have demoed my upstairs and plan to make a studio apartment for my son. Most of the wiring is old (1920s) and in need of updating. Our ground floor lights are currently on knob and tube. My question is "do I need to run the new wiring through conduit or "flex" or can I simply run NM cable on top of the joists in the dead space and then insulate?" I don't want to drill holes through the joists if I don't have to and I don't want to completely remove the knob and tube, just yet, as there are other things that are still on that circuit. I have already run new wiring for the outlets upstairs with NM running through the wall studs. Please advise.....