(HVAC) A downflow furnace takes cool air from the top and discharges warm air from the bottom and are generally placed in an attic.
A furnace that intakes air at its top and discharges air at its bottom.
A furnace with an intake on the top and an air discharge at the bottom.
A furnace that pulls in return air from the top and expels warm air at the bottom.
This furnace sometimes is called a counterflow furnace. The air intake is at the top, and the discharge air is at the bottom.