---
title: "What Is Knob and tube wiring? Electrical Glossary"
description: "Knob and tube wiring is an early wiring method found in very old homes. Single wires run through the air on ceramic supports."
url: https://danielelectric.multisites.ai/glossary/knob-and-tube-wiring
publisher: Daniel Electric
phone: +1-817-481-8606
quote: https://danielelectric.multisites.ai/contact
---

Wiring and circuits

# Knob and tube wiring

Knob and tube wiring is an early wiring method found in very old homes. Single wires run through the air on ceramic supports.

Knob and tube was built to be surrounded by air. The U.S. Department of Energy notes that this older wiring was intended by code to have free air movement to cool the wire as it carries current. Its notice adds that laboratory tests show retrofitting thermal insulation around wiring can cause it to overheat, which creates a fire hazard.

Do not cover it with insulation. Many homes with it also have an [ungrounded outlet](https://danielelectric.multisites.ai/glossary/ungrounded-outlet). Compare [aluminum wiring](https://danielelectric.multisites.ai/glossary/aluminum-wiring). A licensed electrician should evaluate and plan any change. See [electrical warning signs](https://danielelectric.multisites.ai/guides/electrical-warning-signs).

[Daniel Electric can helpResidential electrician](https://danielelectric.multisites.ai/electrician)

## Related terms

-   [Ungrounded outlet](https://danielelectric.multisites.ai/glossary/ungrounded-outlet)
-   [Aluminum wiring](https://danielelectric.multisites.ai/glossary/aluminum-wiring)
-   [Copper wiring](https://danielelectric.multisites.ai/glossary/copper-wiring)
-   [Grounding](https://danielelectric.multisites.ai/glossary/grounding)

## Sources

1.  [U.S. Department of Energy: Weatherization Program Notice 02-5, Health and Safety Guidance](https://www.energy.gov/sites/default/files/2023-06/wpn_02-5_archived.pdf)
2.  [U.S. Department of Energy: Weatherization Program Notice 02-5, Health and Safety Guidance](https://www.energy.gov/sites/default/files/2023-06/wpn_02-5_archived.pdf)

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