Glossary · Fire & electrical safety
Knob-and-tube wiring
Also called: knob-and-tube · K&T wiring
An early type of house wiring that runs separate wires on porcelain knobs and through porcelain tubes, with no ground wire; insulation must not cover it.
What it means
It's found in many older homes, often still live in attics and walls. Insulation shouldn't bury live knob-and-tube wiring, because the wires were designed to shed heat into open air; the national electrical code generally doesn't allow it to be covered by loose, rolled or blown insulation. Have a licensed electrician assess it before anyone air seals or insulates the attic or walls.
Why it matters in an audit
Finding knob-and-tube changes the order of work: the wiring has to be assessed, and often replaced, before attic or wall insulation can go in.