My house is on a slab so my furnace room is in our living space. Pests had chewed away the insulation around the exhaust pipe of my furnace. Over a period of time the condensation around the pipe has caused the ceiling in the hall next to the furnace room to leak. I removed the damaged area and replace the insulation around the pipe. My question is what type of "sheetrock" should I use? Cement board or regular sheetrock? I am repairing the ceiling that was installed in 1972.