Is Knob-and-Tube Wiring Safe in Your Older Home?
Amherst, N.H. – November 01, 2026 -- Homeowners and buyers of houses with knob-and-tube wiring, a system installed from about the 1880s through the 1940s, may face insurance hurdles, sale complications, and safety risks, according to electrical contractor Thomas Reilly of Amherst, New Hampshire.
Reilly's insights appear in a HelloNation article that explains how aging wiring can affect safety, insurance, and renovation plans.
Ceramic knobs and tubes rely on open air to shed heat
The system used ceramic knobs to support separate wires and ceramic tubes to protect them where they passed through wood framing. Rubber and cloth insulation covered the wires, and surrounding air released heat. The design predates today's electrical demands and grounding needs.
These systems have no ground wire. Aging insulation can also crack or fall away, leaving exposed conductors that create shock or fire risks.