As air moves from a supply plenum or main duct into a takeoff it changes direction. Airflow has a hard time making turns at high rates of speed, just as we would driving down the interstate. When we ...

A UL-approved fiberglass plenum box with ceiling radiation damper (CRD) is available in three model styles. The fiberglass plenum boxes are offered in 1- and 1-1/2-inches-thick rigid ductboard with ...