Published August 12, 2026 · 5 min read · MCL Electric
Chicago has some of the oldest housing stock in America, which means two kinds of legacy wiring come up constantly at home sales, insurance renewals, and remodels: knob-and-tube (roughly pre-1950) and aluminum branch wiring (roughly 1965–1973). One is usually a plan-the-replacement situation; the other is often fixable without a rewire. Inspectors flag both. Here's how to think about each without panic — or denial.
Knob-and-tube: what it is and why insurers care
Knob-and-tube ran hot and neutral as separate conductors on ceramic knobs and tubes through joists. Done originally and left alone, it worked — but almost none of it has been left alone for 75+ years. The real problems are what happened since: insulation blown over it in attics (it needs air to shed heat), brittle cracked sheathing, amateur splices, and no ground conductor anywhere. That last one means no three-prong outlets, no GFCI-equivalent protection at the wiring level, and no safe path for a fault.
Insurers increasingly refuse to write or renew policies on homes with active K&T, or demand an inspection letter from a licensed electrician. If you're buying a vintage home in Lincoln Park, Evanston, or Oak Park, assume the question is coming.
Aluminum branch wiring: the 1965–1973 problem
During a copper price spike, builders wired homes with aluminum branch circuits. Aluminum itself conducts fine — the failure point is the connections: aluminum expands and contracts more than copper, oxidizes, and slowly loosens at devices designed for copper. Loose connection → resistance → heat. Most aluminum-wiring fires start at outlets, switches, and splices, not in the middle of a wire run.
The good news: unlike K&T, aluminum wiring often doesn't require a full rewire. Recognized repair methods — properly rated connectors at every device and splice, or replacing devices with CO/ALR-rated ones — address the actual failure point at a fraction of rewire cost. Which method fits your house is a per-home call, made after looking, not over the phone.
How to tell what you have
- Home age: pre-1950 → K&T possible; 1965–1973 → aluminum possible. Later remodels may have replaced some or all of it — partial replacement is the most common thing we find.
- Look at the panel: aluminum branch conductors are marked AL on the sheathing; K&T shows up as single cloth-covered conductors entering the panel.
- Two-prong outlets throughout are a K&T/ungrounded-era tell.
- The definitive answer is a licensed electrician opening the panel and a few devices — that's part of a standard home electrical inspection, not a special order.
Honest triage: what needs action and what can wait
- Act soon: active K&T buried under attic insulation, any warm devices or flickering on aluminum circuits (see our warning-signs ranking), amateur splices, or an insurer deadline.
- Plan for it: K&T still live but accessible and unmodified — replacement can often ride along with a remodel, when walls are open anyway and the cost drops sharply. That's how most of our remodel wiring customers handle it.
- Paired decision: old wiring usually comes with an old panel. If you're touching one, price both at once — the mobilization overlaps. Numbers in our panel upgrade cost guide.
Buying, selling, or got the insurance letter?
We do straight-answer assessments: what you actually have, what the insurer will accept, what has to happen now versus at the next remodel — in writing. Email info@mclelectric.org or call (872) 378-0533. Serving Chicago, Evanston, Wilmette and the North Shore.