Jim writes from my blog host's headquarters city of Toledo, Ohio: "Our house was built in 1912. The attic has 2"X4" ceiling rafters with old cellulose poured between them. My question concerns the electrical wiring: knob and tube, Romex and the newly installed. Can wiring, especially knob and tube and Romex, be overly insulated? The wires run parallel to and across the rafters in some places and perpendicular in others. Would a layer of R-30 fiberglass be too much? Should I try to create air space over the wires and cellulose and under the new insulation? Should the old cellulose be removed first?"

In most cases fiberglass insulation can be placed directly over electrical wires. In the case of true knob and tube wiring, where the wire is not coated with a protective covering, you should not insulate over it. If you are unsure, we recommend having an electrician inspect the existing wiring.