The term upflow in HVAC terms refers to how the air flows from a gas furnace or oil furnace into your ductwork.

By Anne Fonda

In an upflow furnace, the unit pulls in air at the bottom of the unit, passes it over the heat exchanger, and blows the heated air up and out through the top of the unit and into the ductwork. The basement is the most common location for this furnace installation configuration.

An upflow furnace configuration is generally more energy efficient than other configurations because hot air naturally rises. The furnace may also last longer since it doesn’t have to work so hard to heat your home. This can make the upflow configuration ideal for homes in colder climates where you use the furnace more often.

A downflow furnace is the opposite of an upflow furnace as far as airflow. A downflow furnace pulls in cool air at the top of the unit and then heats the air over a heat exchanger. Next, it releases warm air at the bottom of the unit and into the ductwork. An attic is the most likely location for a downflow furnace.

Since heat naturally rises, a downflow furnace must work harder to heat your home. This can lead to early wear and tear and decreased energy efficiency.

In this scenario, the furnace lays horizontally on the floor or base and the air flows in from one side and out the other side. A horizontal flow furnace configuration is most common in attics and crawl spaces.

The best airflow configuration is the one that works best with where you need to locate your furnace. If your home has a basement, an upflow furnace would be most efficient. If you have to place the furnace in the attic, a downflow furnace configuration might be best. If you need to install the furnace in a crawlspace, a horizontal configuration might be optimal, depending on the space available.

An experienced HVAC company can help you determine the best location and airflow configuration for your furnace so that it can operate most efficiently.

There are many factors to consider when it’s time to choose a new furnace or HVAC system, including:

• Energy efficiency/AFUE
• Sizing
• Furnace cost
• Fuel source
• Location
• Airflow configuration

As you can see, several factors rank higher in importance than airflow configuration. A reputable HVAC contractor can help you find the right furnace and the right location and configuration to work for your home and your family.

Use our Buyer’s Guide for some tips to help you select the right system.

If your furnace is aging out or repairs are costing more and more every year, it may be time to think about furnace replacement. To make the purchasing process as simple as possible, we believe in being upfront about the cost of our furnaces. You can find average furnace prices in our pricing guide and on individual product pages.

The installed price of your new furnace will vary based on several factors including the size and layout of your home, where you live, the furnace you choose, and the complexity of the installation process. Contact a local Trane Comfort Specialist™ to get a custom quote for furnace replacement cost for your home.

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Anne Fonda, Content Writer

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A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism.

When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by  John Kim, Senior Product Manager, Furnaces