Gerry writes from Tarrytown, New York: "I installed your R-19 faced insulation between the joists in my unfinished attic a few years ago, vapor barrier down, and laid R-25 unfaced at a right-angle on top of that. Big difference in the heating bills! My question: I recently rolled back some of that insulation, and see that wherever the paper facing is in contact with Romex NM wiring, a brown, gummy, creosote-like residue appears on the cable sheating and the paper. What is the cause of this - and is it something I need to be concerned about?"

Answer: Most likely what is happening is that as the wire heats up during use it warms the paper facing enough for the asphalt coating on the paper to bleed through. The easiest way to prevent it from happening is to remove the paper in the area of the wire. I also suggest having the wiring checked to make sure the circuit is not overloaded and/or the wiring is not faulty.