Your home furnace air intake location depends on where the furnace is. There are two types of airflow furnaces, a downdraft or downflow furnace and an updraft or upflow furnace. The flow of air that leaves the furnace determines what type it is. If airflow comes in from the top, it is a downdraft or downflow furnace. If return air comes in at the bottom, it is an updraft or upflow furnace.
Down Draft Furnace
A downdraft furnace uses cool air, claimed at the top of the unit, heats it and then blows it into ductwork beneath the furnace. Downdraft furnaces are generally located on a living floor of a home. The ductwork goes below the flooring and the cold air intake on the furnace is at the top.
Up Draft Furnace
An updraft furnace takes in cool air at the bottom of the unit and, once it is heated, blows it into ductwork above the furnace. This type of furnace is commonly located in basements, and the air intake is at the bottom of the unit.
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