Can old fabric-wrapped wiring in a Calgary home cause a fire?

Yes, fabric-wrapped wiring in a Calgary home is a genuine fire hazard and should be professionally assessed as soon as possible. The insulation on this wiring has typically been degrading for 60 to 100 years, and Calgary's unique climate conditions accelerate that deterioration in ways that make it more dangerous here than in many other Canadian cities.

What Fabric-Wrapped Wiring Actually Is

The wiring you're describing is almost certainly knob-and-tube (K&T), the standard residential wiring method used from roughly the 1880s through the 1940s. It consists of individual copper conductors wrapped in rubber insulation and then a cotton or cloth braid, routed through ceramic knobs (which hold the wire away from framing) and ceramic tubes (which protect it where it passes through joists and studs). Some homes also have early rubber-insulated wire without the knob-and-tube routing — just cloth-jacketed conductors stapled to framing — which is equally problematic.

The core issue is the rubber insulation underneath that fabric jacket. Rubber from this era was never designed to last a century. It becomes brittle, cracks, and crumbles — sometimes to the point where the bare copper conductor is exposed inside your walls and attic. When bare conductors contact wood framing, insulation batts, or each other, the result can be arcing, heat buildup, and fire.

Why Calgary Makes This Worse

Calgary's chinook cycles are particularly hard on old wiring. The repeated rapid temperature swings — sometimes 20 to 30 degrees Celsius within a few hours — cause constant expansion and contraction in the wiring, connections, and the framing around it. Over decades, this mechanical stress accelerates cracking in already-brittle rubber insulation and loosens the connections at junction points. Electricians in Calgary see more deteriorated K&T than you'd expect to find in a city with a more stable climate.

The extreme cold from November through March also matters. When old rubber insulation gets cold enough, it becomes rigid and loses what little flexibility it has left. Any movement — vibration from a furnace, someone walking across the floor above — can cause cracked insulation to shed entirely.

There's also an insulation problem specific to older Calgary homes that have been upgraded for energy efficiency. Knob-and-tube wiring was designed to dissipate heat into open air. When homeowners or contractors blow insulation into attics or walls without first removing the K&T, the wiring loses its ability to cool itself and can overheat at normal load levels. This is a code violation and a documented fire cause. If your attic has been insulated and K&T is still present, this is an urgent situation.

What Alberta Code and Insurers Say

The Canadian Electrical Code as adopted in Alberta does not require you to immediately remove knob-and-tube wiring that is in good condition, but "good condition" is the critical qualifier — and determining that requires a licensed electrician with a permit to open walls and inspect the actual state of the insulation. In practice, most Alberta home insurers have become increasingly reluctant to cover homes with active K&T wiring. Many will either refuse coverage outright, charge significantly higher premiums, or require a licensed electrical inspection as a condition of the policy. If you're buying or selling a home in Calgary with K&T present, expect it to come up in the home inspection and the insurance application.

Practical Steps to Take Now

Start with a licensed electrician's inspection — not a home inspector's visual assessment, but an actual electrical inspection where the electrician opens junction boxes, checks the attic, and evaluates the true condition of the wiring. This typically costs $200 to $500 and gives you a real picture of what you're dealing with. If the wiring is actively deteriorated, cracked, or has been covered with insulation, remediation should not wait.

Full knob-and-tube removal and rewiring in a Calgary home runs approximately $7,000 to $13,000 for a smaller bungalow and $15,000 to $26,000 for a larger two-storey, depending on wall accessibility and the scope of the project. A permit is required, and a Safety Codes Officer will inspect the completed work — keep that compliance document permanently with your home records.

In the meantime, do not add load to circuits you suspect are K&T — no space heaters, no high-draw appliances plugged into older outlets. If you smell burning, see flickering lights, or notice warm outlet covers, treat it as an emergency and call a licensed electrician immediately.

Need help finding a licensed electrician to assess your wiring? Calgary Electrical Services can match you with local professionals at no cost — or browse the Calgary Construction Network directory at calgaryconstructionnetwork.com/directory?trade=electrical.