Dear Bruce,

I know that my house still has some old knob-and-tube style wiring. What does that mean and should I have it replaced?

Bruce Says:

Knob-and-tube is a wiring method employed starting in the early 20th century that used fabric covered single conductors strung through the ceiling like a railroad track and supported by porcelain knobs. There is no grounding conductor present only a hot and neutral. The wiring was often installed by the carpenter building the house.

There have been many studies done to determine the amount of degradation that the conductor incurs at the point where it is wrapped around the knob to feed an outlet or change direction along its path through the house. Also ambient temperature (120 degrees in the attic) has a negative effect. All of this information and much more is available online if you can keep your eyes open long enough to read it.

The long and short of it is that yes, heat degradation of the insulation protecting the conductor does occur in attics and at the point of wrap on the knob. Many insurance companies will not insure a home containing this wiring method because of these results. So the short answer is yes, replace it all along with the old fuse box and “A” base meter socket. We can help.

Give us a call and we will review your options with you.