From roughly 1965 to 1973, aluminum was used for residential branch circuit wiring as a substitute for copper — at the time it was cheaper and seemed like a reasonable alternative. Many Denver homes built during that era in neighborhoods like Montbello, Green Valley Ranch, and parts of Lakewood and Westminster have aluminum branch wiring today. It is not automatic cause for panic, but it is a condition that requires specific management.
The problem is not that aluminum conducts electricity poorly. It does not. The problem is that aluminum oxidizes differently than copper, and it expands and contracts more under heating and cooling cycles. Over decades, those cycles loosen connections at outlets, switches, and fixtures — and a loose aluminum connection is a heat source. The Consumer Product Safety Commission documented a significantly elevated fire risk in aluminum-wired homes versus copper, concentrated at device connections, not in the wire runs themselves.
What a home inspection typically says
A standard home inspection flags aluminum branch wiring and recommends 'evaluation by a licensed electrician.' That evaluation should include pulling outlet and switch covers to assess the connection condition, checking for signs of overheating (discolored wires, melted plastic, char marks at device screws), and reviewing what mix of devices are currently installed. Most aluminum-wired homes in Denver have had at least some outlets swapped at some point — the question is whether they were replaced with the right devices.
Ordinary outlets and switches are rated for copper only (marked CO or CU on the device). Installing one on an aluminum wire creates exactly the dissimilar-metal contact point the CPSC warns about. This is the hidden danger in many 1960s Denver homes: the wiring itself may be fine, but the devices may have been swapped over the years without anyone checking the compatibility rating.
The two CPSC-approved remedies
There are two solutions recognized by the CPSC and permitted under the NEC for existing aluminum branch wiring. The first is CO/ALR-rated devices — outlets and switches specifically rated for aluminum connections — installed at every device location. In Colorado, CO/ALR outlets run about $15–$25 each, and swapping a full house typically costs $800–$2,500 in labor depending on how many devices there are.
The second option, often preferred for long-term reliability, is pig-tailing: splicing a short length of copper wire to the end of each aluminum run using an AlumiConn or IDEAL 65 connector — the two connectors specifically listed for aluminum-to-copper pigtailing under the CPSC's guidance. The devices are then connected to the copper pigtail in the normal way. The connectors seal out air to minimize oxidation at the splice. This approach costs more per outlet ($40–$80 per connection in labor) but eliminates the aluminum-to-device interface entirely.
Neither solution requires rewiring the house. Full replacement with copper is an option, but it is also an order of magnitude more expensive and not required by code for existing wiring. If you own a Denver home from this era and have never had an aluminum wiring evaluation, the cost of an inspection and a written assessment is minimal compared to the cost of ignoring it.