What Is Aluminum Wiring?
Between the mid-1960s and mid-1970s, rising copper prices led many homebuilders to seek a more affordable alternative for residential electrical systems. As a result, single-strand aluminum wiring was commonly installed in branch circuits—the wires that supply power to outlets, switches, and lighting fixtures throughout a home.
Aluminum is an excellent electrical conductor and remains widely used today in utility power lines and large electrical service feeders. However, its use in standard residential branch-circuit wiring introduced safety concerns that were not fully understood at the time.
Why Is Aluminum Wiring a Concern?
Aluminum wiring does not typically fail on its own. The primary risk occurs at connection points, where the wire attaches to outlets, switches, breakers, and junction boxes. According to the Consumer Product Safety Commission (CPSC), homes with aluminum branch-circuit wiring are significantly more likely to experience fire-hazard conditions at electrical connections than homes wired with copper.
Several characteristics of aluminum contribute to these risks:
Thermal Expansion and Contraction
When electrical current flows through a wire, it heats up and expands. As it cools, it contracts. Aluminum expands and contracts more than copper, causing connections to gradually loosen over time. This process, sometimes called “creep,” can reduce the quality of the connection and increase resistance.
Oxidation
When exposed to air, aluminum naturally forms a layer of aluminum oxide. Unlike the oxide that forms on copper, aluminum oxide is highly resistant to the flow of electricity. This resistance generates heat at connection points, which can lead to overheating.
Galvanic Corrosion
When aluminum comes into contact with dissimilar metals, such as copper or brass, an electrochemical reaction can occur in the presence of moisture. This reaction can corrode the connection, increasing resistance and further reducing reliability.
Softness and Brittleness
Aluminum is softer than copper and can be more easily damaged during installation. Repeated bending can also cause the wire to become brittle and break, potentially creating dangerous arcing conditions.
How Electrical Fires Can Develop
Loose connections caused by thermal expansion, combined with resistance from oxidation or corrosion, can generate excessive heat in a small area. Over time, temperatures may become high enough to damage outlets, melt insulation, create electrical arcing, or ignite nearby combustible materials. In some cases, these hazards can develop before a circuit breaker detects a problem.
Warning Signs of Aluminum Wiring Problems
If your home contains aluminum wiring, watch for the following warning signs:
- Flickering or dimming lights
- Outlets or switches that feel warm or hot to the touch
- A burning plastic or electrical odor near receptacles or switches
- Sparking when plugging in appliances or using switches
- Intermittent power loss or appliances that unexpectedly shut off
- Unexplained static or interference on electronic devices
How to Verify if Your Home Has It
If your home falls into the target age bracket and location, you can check without putting yourself in danger:
Check the Basement or Attic: Look for exposed electrical cables running along the joists. Look closely at the plastic jacket. If you see “AL”, “ALUM”, “ALUMINUM”, or the brand name “COALUM” stamped into the plastic, you have it.
Review Your Home Inspection Report: If you bought your home recently, Colorado home inspectors are highly trained to look for this. Check the “Electrical” section of your report to see if it was flagged.
