how do you know when you need to change your insulation?
I have a 1933 house and in the attic is cotton (or wool, i can't tell) insulation that is just loose on the floor/second floor ceiling. I don't know when it was put in since it was here when I bought the house in 2003. I have no idea if there is insulation in the walls at all, on the first and second floor, and they are plaster on steel lathe so I'm not going to dig a hole in them to check, unfortunately. so, given that, should I just assume I should swap out the attic insulation for R38, or put it ontop (with the backing off)?