[ Page 1 of 8 ]

By Alex Wilson

Even the greenest of architects seldom give much consideration to wiring in buildings. How significant can wiring be? It’s just a small fraction of what’s installed compared to other building materials—and don’t fire codes more or less dictate what can be used? But some sleuthing about how wiring is made and used in buildings sheds light on a highly complex issue and points up a need to pay closer attention to today’s practices, from environmental, health, and safety standpoints.

All modern buildings, of course, require wires and cables for power distribution and to carry voice and data signals. The term wire refers to an individual strand of material that conducts electrical current, whereas cable refers to two or more wires twisted together. Virtually all wire and cable used in buildings is wrapped in plastic insulation, and most of these components are made by bundling multiple insulated wires together, sheathing them in an additional outer jacket. Insulated wire and cable come in a large variety of types, and there are many performance standards and ratings that govern how and where they can be used. In the U.S., insulated wire and cable represents an annual $20.5 billion market that is projected to grow by more than 5 percent per year through 2006, according to a 2002 report from the Freedonia Group. There are an estimated 11 million miles of data cabling in U.S. buildings today.

ADVERTISEMENT

In general terms, power cables in commercial buildings must be either sheathed in metal armor (BX cable) or protected within metal conduit. In residential buildings, power cables can be jacketed in plastic; this type of cable is commonly referred to by a trade name, Romex (made by the Southwire Company). Data or communications cables can be installed in most buildings without metal protection, but a specialized plenum rating is required for installation in ceiling and floor plenums.

Many materials coming together

Copper is the dominant conductor used in insulated building wire and cable. Though less common, aluminum wire is also used; it’s lighter and less expensive than copper, but also less conductive, so more material is required for the same electrical capacity. Fiber-optic cable, which is made of glass, is increasingly used for data and communications applications commonly served by insulated wire and cable. Fiber optics transmit light signals instead of electricity to carry data—and they’re lighter, less expensive, and more energy-efficient than copper for data transmission. Because they don’t carry electric current, insulation requirements are not as great as for metal conductors.