Check wiring before installing insulation

Question: The house I own is more than 100 years old, with the old lath boards, plaster, and old, drafty windows. So insulating it is important. One part of the attic has old, blown-in insulation between rafters. It comes up to the top of the rafter. There is some of the old electrical wiring (separate lines for the black and white) in the attic. Should I use the blown-in insulation or pink rolls? Is there a difference? The second story is often cool in the winter, so how much should I use?
-- J.B., Ann Arbor

Answer: Before you start insulating, you need to determine what to do about the older style knob-and-tube wiring in your attic. That system may still be perfectly safe -- if it was properly installed, is in good condition, and hasn't had improper alterations to it over the years. However, the National Electrical Code requires that it be used the way it was originally designed -- and that means the wires have to be ``air-cooled.'' In other words, you can't pile insulation on top of or around it.