I am wiring a house with Dietrich TradeReady joists.The openings in the joists are 6x9 inches and the edges are rolled 90 degrees.The metal edge is very sharp and I feel that an insulator is necessary. Is there a special insulator available for these joists? Or is there another way to do it?
I don't have much experience with NM, or the joists you're talking about. If there are no special insulators available, maybe a piece of garden hose cut to length, slit lengthwise and slipped onto the sharp edge.