Buying a older home
If you are buying a home that was built prior to 1950, it may have knob and tube wiring. Even though this technology is older it is still capable of carrying electricity throughout your home. There are additional factors that homeowners should know about when buying or selling a home with knob and tube wiring.
What is Knob and Tube Wiring?
The system uses porcelain insulators (knobs) for running wires through unobstructed spaces. Porcelain tubes protect wires that run through studs and joists. The two electrical wires are wrapped in a rubberized cloth, and are run suspended through the walls. In contrast, modern systems have a third additional "ground wire" and three-prong outlets that add an extra measure of safety.
Is it Unsafe?
Installations have to be evaluated on a case by-case basis. Safety usually depends on the history of modifications and upgrades. While an electrician can do a proper splice, home inspectors should be able to find inappropriate splices which can create a serious safety hazard. Knob and tube wiring was designed to let heat dissipate to the surrounding air so most energy efficiency upgrades involve insulating previously uninsulated walls. Upgrading the insulation also requires replacement of the wiring in the home.
Home owners Insurance
As existing knob and tube wiring gets older, insurance companies may deny coverage due to increased risk. In fact, many home insurance companies will not write new policies on homes with knob and tube wiring. If you are buying a home, you may have to upgrade part of or all of the system. Some insurance companies will insure you through the transaction but will require you to upgrade within a defined period of time. I have a neighbor that purchased a older home, her inspector did not mention knob and tube wiring in his report. After her purchase, she had to spend thousands more than expected because of this over-site by her inspector.
Updating the Wiring
It's often not too expensive if you only have a few knob and tube circuits to replace. But, if the home has knob and tube wiring throughout, an upgrade may involve more than just replacing existing circuits. It may require upgrading the breaker panel which can be expensive. In an upgrade, the wiring will be updated to meet today's standards. In the end, it is generally well worth the expense to upgrade to the safer modern electrical system.
We had our 1926 home completely rewired. I asked other home owners who they have used. I check online services like Angie’s list, https://www.angieslist.com/AngiesList/Login.aspx to see what other home owners said about the companies. Do your home-work before you hire a company. Remember, you can never have too much information.