Up-flow vs. Down-flow Furnaces: What's the Difference and Does it Matter?

Up-flow and down-flow; these descriptive words identify the direction air moves through a furnace and how that furnace is configured in the space it occupies. The location of the furnace within your home determines whether the best choice is up-flow or down-flow furnaces. Now, you might be wondering, why you want or need to know which way the air is flowing through your heating system? The thing is, furnaces and evaporator coils are designed and built to be used in specific positions within the space they are installed in and should you need to purchase a replacement unit you need to be certain of the appropriate configuration. At HVACDirect, we are here to ensure our customers avoid inconvenience and costly errors by helping them buy what they need. Technology is so advanced, and product selections so specialized that the choice is no longer so much about getting the one best product as it is about getting the best product for the circumstances in question. No one product is the best choice for everyone.

Identifying Your Furnace Type

An up-flow furnace means the air is pulled into the bottom of the air handler and, once heated, passes out near the top of the unit. This type of system is most commonly installed in a basement. These systems are energy-efficient because the natural propensity of heat to rise assists with the heated air being pushed upward into the duct system of the home, making this an attractive configuration. Additionally, many people prefer a room heated from the floor upward rather than from the ceiling downward. A down-flow unit, almost the complete opposite, means the air enters the furnace at the top and flows out at the bottom of the unit and downward to the duct system after being heated. These units are most often installed in a closet or similar kind of space. They can be placed in an attic, a garage, or on the main level of a home.

One Against the Other: Which is Better for Your Home? Up-flow or Down-flow?

Cost wise, the unit itself for an up-flow or down-flow furnace is comparable. However, when it comes to installation, a down-flow will likely cost more.

Additionally, down-flow furnaces have stricter requirements, then up-flow furnaces, to ensure safety regarding combustible floor materials involved in a down-flow unit installation. This means that either the floor must be made of noncombustible material or the furnace must be installed with a subbase configuration. Flooring materials like linoleum or carpeting can create fire hazards in crawl spaces, attics, and closets. When you are looking at a down-flow furnace, a garage might be the least complicated installation because most garages have concrete flooring, which is not considered a combustible material. Another disadvantage of a down-flow furnace is that unlike an up-flow furnace, down-flow furnaces fight against the natural upward flow of warm air. The requirement to must push air into the duct system from above contributes to loss of efficiency in these units. However, it is not all bad news when looking at down-flow furnaces, one very attractive feature of a down-flow unit is that it can fit in nearly any home, which is useful for homes that do not have a basement or crawl space. While our discussion here is not really about horizontal configurations we do want to make you aware that this type of installation exists and is a viable option for some homes where space is at a premium. Usually installed in an attic or crawl space, a horizontal configuration is an up-flow or down-flow unit laid on its side with air flowing in one end and out the other. Typically horizontal configuration is not needed as nearly any home can use a down-flow furnace, and those with a basement or adequate crawl space can choose an up-flow unit. At HVACDirect, we are eager and able to help customers make the right choice by providing them with the information needed to make the best decision for their space and needs. Contact us today.