In some ways, knob and tube writing is safer than modern wiring methods as long as it’s carefully installed and maintained. Among other things, knob and tube wiring is designed to freely dissipate heat to the surroundings. Open airspace is considered highly important. Hence, the wires are widely separated from each other by 4 to 6 inches, and this allows the heat to readily dissipate into the air. Clearly, insulation disrupts this process and causes the heat to build up. With that said, knob and tube writing is often seen as a safety hazard as it can cause fires. Knob and tube wiring is not inherently dangerous, but it tends to deteriorate over time. Moreover, past owners might have added some modifications to the system that make it dangerous. Although some insurance companies make exceptions for houses with inactive K&T wiring systems, most insurance companies refuse outright to underwrite homes with active systems. For most interested buyers or sellers, replacing knob and tube wiring is the only way to go. So before you buy that old house you had set your eyes on, have it inspected first by a qualified electrician. If there’s an active knob and tube wiring system, have it removed only by trusted technicians.