From a global perspective, the use of aluminium conductors in building wire is very limited. Aluminium is not accepted at all in many markets and in others it is only used a little, even though its use may in some localities be permitted in building codes and wiring regulations. Even in some markets where aluminium building wire was widely used at one time (e.g. India), copper building wire is now generally preferred. Despite the major increase in the cost of copper over the last two years, there are few signs that aluminium is making a definite comeback in building wire.
The lack of acceptance of aluminium in building wire is usually attributed to bad experiences with aluminium wires that were reported in the 1960s and 1970s. In North America poor quality joints in aluminium wiring were identified as a possible cause of some house fires. The type of aluminium originally used in building wire (EC grade, the same as power cables) had a higher rate of creep than copper. Aluminium was also incompatible with steel screws used in jointing accessories. Poor contact at joints allows an oxide layer to form, and the temperature rises due to the higher resistance. Even though alternative aluminium alloys and improved accessories for building wire were developed after these potential problems were understood, there has been no major swing back to aluminium building wire, despite the apparent cost advantage of aluminium over copper.
In North America some cable companies have been actively promoting the virtues of aluminium conductors in building wire. It can be useful to offer customers an alternative to copper wire when prices are high, though there are other reasons why a cable supplier might want to promote aluminium conductors over copper. Firstly, groups that have upstream interests in production of refined aluminium and wirerod would want to encourage greater consumption of aluminium. Secondly, there may be some competitive advantage in supplying building wire using aluminium, rather than copper. Not all companies can offer a full range of building wires, both copper and aluminium, so those with the full range of both may prefer to promote aluminium products where the competition may be less intense and margins potentially higher than in the established product, copper building wire.