In the late sixties, and early seventies aluminum wiring began to be used because most available copper was going to the Vietnam war effort. However, aluminum wiring is not ideal for small home electrical systems. The electrical devices at that time were not designed to handle the high temperature coefficients of aluminum wiring. Aluminum wires can also expand in diameter and length as they get hot, they can actually back out the screw terminals, causing a loose connection. This, in turn, can cause heat, which can ultimately lead to a fire.
After problems with aluminum wire termination became known—including one notable house fire—the UL (Underwriters Laboratories) and other agencies adopted new safety regulations and put more restrictive standards in place. However, many homes from the 60s and 70s still do not have safe aluminum wiring terminations. But there are a number of ways to solve this problem without having to rewire a home.
Consumer Safety Council Recommendations
According to the Consumer Safety Council, there are only two approved methods that splice aluminum wire to copper wire:
These standards have caused acceptance problems with home inspectors and insurance companies, which has led to homeowners paying 2 to 4 times as much as they should to have their aluminum wiring terminated.