Downflow

The term downflow, when used in HVAC terminology, refers to how the air flows from a gas furnace or oil furnace into your ductwork. A downflow furnace takes in cool air at the top and heats the air over a heat exchanger. Then, it releases warm air down at the bottom. This warm air then circulates through the ductwork system to heat your home. An attic is the most likely location for a downflow furnace.