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Pop Quiz: October 2007

Test your knowledge of construction terms.

  • The “R-factor” (or R-value) of a building material is based on its thickness in centimeters — for example, R-11 fiberglass insulation is 11 centimeters thick, etc.
  • Drywall, gypsum, and sheetrock all mean the same thing.
  • Three-phase electrical building power actually has four conductors.
  • “Plenum” means a specific type of cable that can be used in ceiling spaces.

1. FALSE. The R-value refers a material's thermal resistance factor. The higher the R-value, the greater resistance to the flow of heat.

2. FALSE. Technically, drywall refers to the system of interior wall finish using sheets of gypsum board and taped joints. Gypsum is the name of the mineral composed of hydrous calcium sulfate, which is the main component of the wall-board used in drywall construction. Sheetrock is a registered brand name belonging to the United States Gypsum Co., but like Kleenex and Band-Aid, it's become a generic term.

3. TRUE. Three-phase consists of four wires and is used in industrial and commercial applications, especially those requiring large motors. It consists of three hot wires and one ground wire. The voltage in each hot wire is out of phase with the others by 1/3 of a cycle, as if produced by three different generators.

4. FALSE. While there is a cable known as plenum cable, the word “plenum” refers to the space itself. Plenum comes from a Latin term, plenus, which means full. In buildings, it refers to a chamber that's full of air, typically between the structural ceiling and the suspended ceiling or under a raised floor. Plenus is also the root of the words plenty and replenish.

Source: Peter R. Brown Construction, Online Etymology Dictionary.

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