What is a Plenum ceiling?
According to the National Electric Code (NEC) a plenum is a “compartment or chamber to which one or more air ducts are connected and [which] forms part of the air distribution system.” In other words, the open space above your ceiling extends above other rooms in the same building or is open to ducts that connect it to other parts of the building. In a plenum ceiling air can circulate through the air ducts to the whole building.
