Unless you live in a home that was built before 1930 (like homes in the Westport, Mission Hills and Brookside areas) you may not be aware of knob and tube wiring. This type of wiring was used between 1880- 1930 as an electrical wiring system. The Knob and Tube description is used to explain the porcelain knob insulators that are nailed down and used to support the single insulated copper conductors as they pass through walls, ceilings and joists where they are protected by insulating tubes. Where the conductors enter the device (light or wall outlet) the connection is protected by an insulating sleeve called a loom. This loom was first made of an asphalt cotton cloth and rubber eventually replaced the cotton.
Knob and Tube wiring became less desirable as it was very expensive to install compared to the newer technology of power cables. Knob and Tube is no longer permitted in the U.S. (except in rare industrial and agricultural environments).
If you compare the energy needs we have today with the energy needs 80 years ago, the ability to safely add more circuits to this kind of a system poses dangers and challenges. Adding circuits to the knob and tube system may pose safety hazards as blown circuits and over loaded circuits which cause more heat and friction and the tubes and their insulation becomes brittle and may pose a fire hazard. The cotton insulation is also a treat for animals. The less insulation around the tubes, the more heat is exposed which in turn creates more fire hazards.
To properly evaluate the Knob and Tube system in an attic you have to remove the insulation. Simply adding more insulation to an attic that has knob and tube wiring may result in a fire if the insulation around the wires has deteriorated or been chewed away by rodents. Have an insulation contractor safely remove the insulation before the electrician evaluates and changes the old wiring system with a new one. The Contractor can then apply a more energy efficient type of insulation to your attic.
Know the dangers before you sell
If you are looking to sell a home that has knob and tube wiring, many insurance companies will not insure the home to its full value. Always look at all your options before making significant changes to any system in your home. Make sure you are well informed about all your options and have consulted with knowledgeable insulation and electrical professionals and how each will interact with the other.
Knob and Tube wiring certainly was useful in its day. Today, it may well pose dangers and fire hazard. Call an electrician (and possibly a Fire Safety Professional) and then contact Murray Insulation to remove and then re-apply energy efficient foam or blown in fiberglass insulation in your attic.