What Is the Square-Shaped Pipe in the Attic?

Air Ducts

• In many cases, what appears to be square pipe in the attic is likely to be an air duct. Many air ducts are round. In some instances it could be more advantageous to use square ducts, whether it be for economic reasons or possibly for space considerations. Air ducts generally consist of a supply air duct that supplies air to the rest of the house and a return air duct that circulates the air back to the furnace or air conditioner where it is again heated or cooled.

Wireways

• Square duct wireways also appear to be square-shaped pipes. These are often located in the attic as well. A square duct wireway is basically a protective duct through which wires and other electrical equipment, such as branch circuits and conductors, are fed. These wireways help protect these electrical components from dust, moisture and other potential hazards.

Advantages

• Square-shaped ductwork has advantages over round ducts. For instance, square ducts can be space savers and can be placed into corners where round ductwork cannot. Rectangular ducts can be placed between studs as well. These ducts are usually sturdy and last longer than flexible ducts, which are generally round. Round metal ducts have one major advantage over a square duct pipe in that they don't restrict airflow as much, thus allowing the heating and cooling system to work with greater efficiency.

Disadvantages

• Square ducts and round ducts alike have one disadvantage compared with flexible ducts. Both of these types of ducts must be insulated when they are installed, while flexible ducts tend to have the insulating material built in. In general, there are few disadvantages to using these types of ducts and it is not uncommon to see either the square or rounded version in the attic.