Can insulation cover knob-and-tube wiring?

Insulation around knob-and-tube wiring can trap heat near the conductors. An electrician can assess the wiring and insulation together before you plan attic work.

Does homeowners insurance cover a house with knob-and-tube wiring?

Homeowners insurance rules for knob-and-tube wiring depend on the insurer and the policy. Ask your insurer how the wiring affects coverage before you make a decision.

What changes the price of knob-and-tube wiring replacement?

The price of knob-and-tube wiring replacement depends on the wiring's reach and how hard it is to access. Request an estimate that explains the wiring work and any wall repairs.

Glossary

What Is Knob-and-Tube Wiring?

Knob-and-Tube Wiring is an older electrical wiring system that carries power through separate insulated conductors in a building. Porcelain knobs support the wires, and porcelain tubes protect them where they pass through framing. You may find this wiring in the walls, attic or basement of an older home.

Local relevance: Pittsburgh has older homes where original wiring may remain alongside later electrical updates, so a replacement plan may need to account for both.

Quick Facts About Knob-and-Tube Wiring

Category: Residential electrical wiring
Used for: Supplying power to household circuits
Common confusion: Visible porcelain parts can remain after wiring is disconnected
Also called: Knob and Tube, K&T wiring
Often discussed with: Knob-and-Tube Wiring Replacement, Whole-House Rewiring

Key Takeaways About Knob-and-Tube Wiring

Its conductors typically run apart rather than inside a shared cable.
Replacement can involve opening walls to reach wiring.
Porcelain parts alone don't prove that wiring is active.

How Knob-and-Tube Wiring Works

Two men inspect a wall cable beside a brick wall inside a dim room

Knob-and-Tube Wiring carries current along a hot wire to a light or outlet. A separate neutral wire provides the return path. The wires follow routes through the building and connect at points along the circuit. Related service: Knob-and-Tube Wiring Replacement.

Related glossary terms: Branch Circuit, Neutral Wire, Electrical Grounding.

Knobs hold the conductors away from wood framing. Tubes form a protective passage through framing. The wire covering also helps separate the conductor from nearby material.

Modern cable typically groups conductors inside an outer covering. Older knob-and-tube circuits generally don't include a grounding conductor. A grounding conductor gives fault current a path back to the electrical system.

A home can contain both older wiring and newer cable. A connection between them may be hidden in a wall or ceiling. Tracing the circuit helps show which outlets and lights it serves.

Hands use a screwdriver to adjust an electrical wire held by ceramic clips under wooden beams

From the Electrician Pittsburgh team

When we plan knob-and-tube replacement, we trace the affected circuit and look at where it serves the home. We also check where older wiring meets newer wiring. That helps us plan the replacement route and identify places that may need access.

Knob-and-Tube Wiring in Practice: A Real-World Example

A Pittsburgh homeowner finds old wiring near an attic light and wants it replaced. The replacement plan follows the circuit to its outlets and accounts for access through the ceiling.