Room temperatures vary greatly... For instance here in Florida my house stays in the mid to upper 70's year round, while up north in the winter room temperatures can easily be 20-30 degrees cooler.
Room temperature is very important when you are using a rack as it determines the cool side temperature of the tubs. Heat tape doesn't increase the temperature of the air inside the tub, just the surface temperatures. In many cases people with racks need to have a space heater by the rack to boost the temperature in that part of the room. You need to keep the air temperature above 75, but closer to 80 is preferred.