
An upflow furnace is a heating unit set up so it draws cool air in near the bottom and blows heated air out the top into supply ductwork. The blower sits below the heat exchanger, so warm air rises naturally into ducts that run overhead, through the ceiling, or to an upper floor. You will usually find this orientation in a basement or a ground floor closet where the duct system feeds the levels above it. It is one of the most common residential furnace configurations.
/ˈʌpˌfloʊ ˈfɜːrnɪs/
An upflow furnace is a heating unit set up so it draws cool air in near the bottom and blows heated air out the top into supply ductwork. The blower sits below the heat exchanger, so warm air rises naturally into ducts that run overhead, through the ceiling, or to an upper floor. You will usually find this orientation in a basement or a ground floor closet where the duct system feeds the levels above it. It is one of the most common residential furnace configurations.
What is an upflow furnace?
An upflow furnace takes in cool air near the floor and blows heated air upward into ductwork that runs overhead or to upper floors. The blower sits below the heat exchanger, and the unit is typically installed in a basement, closet, or ground floor utility space.
Source: The Cooling Company

In a two story Las Vegas home, an upflow furnace often lives in a downstairs closet or garage utility space and pushes warm air up through ducts hidden in the walls and ceilings to reach the bedrooms above. Because return air enters low and supply air exits high, the layout matches homes where duct trunks run overhead rather than under a slab.
Keep the return air path clear and change the filter every 30 to 90 days. An upflow unit pulls air in low, so a blocked return or clogged filter starves the blower and drives up your energy bills.
“Keep the return air path clear and change the filter every 30 to 90 days. An upflow unit pulls air in low, so a blocked return or clogged filter starves the blower and drives up your energy bills.”
Many modern furnaces are multi position, meaning the same cabinet can be certified for more than one orientation, such as upflow and horizontal or even all four positions. Some models are rated for only a single direction, so you should always confirm the manufacturer's approved installation positions before the unit is mounted.
How do I know if I have an upflow furnace?
Look at where the warm air leaves the unit. If the supply ducts connect at the top, the return connects near the bottom, and the cabinet stands upright, you have an upflow furnace.
Is an upflow furnace better than a downflow?
Neither is better; the right choice depends on your ductwork. Upflow suits homes with overhead or upstairs ducts, while downflow fits homes where the ducts run under the floor or a slab.
Can any furnace be installed as an upflow?
No. Many furnaces are multi position and support upflow or horizontal, but you must confirm the model rating. Installing a unit in the wrong orientation can void the warranty and hurt performance.
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