The term downflow, when used in HVAC terminology, refers to how the air flows from a gas furnace or oil furnace and into your ductwork.
By Anne Fonda
A downflow furnace takes in cool air at the top and heats the air over a heat exchanger. Then, it releases warm air down at the bottom. This warm air then circulates through the ductwork system to heat your home. An attic is the most likely location for a downflow furnace.
Since heat naturally rises, a downflow furnace has to work harder, leading to more wear and tear. A furnace with this airflow configuration may also be less energy efficient.
An upflow furnace is the polar opposite of a downflow furnace concerning airflow. In an upflow furnace, air is taken in at the bottom of the unit, passes over the heat exchanger, and flows 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 is generally more energy efficient than its downflow counterpart. The furnace may also last longer since it doesn’t have to work so hard.
In a third airflow configuration, the unit is lying on its side 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 you have a basement, an upflow furnace would be best. If you have to place the furnace in the attic, a downflow furnace configuration would be best. If you need to place the furnace in a crawlspace, a horizontal configuration might be optimal, depending on the height of the crawlspace.
There are many factors to consider when choosing a new furnace or HVAC system. They include:
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.
Trane believes in making the purchasing process as simple as possible. That includes being upfront about the cost of our furnaces. You can find average furnace prices in our pricing guide and on individual product pages.
Please note, that the installed price of a furnace depends on several factors including where you live, the unit you select, the size of your home, and the complexity of the installation process. That’s why we recommend talking to a Trane Comfort Specialist™ to get a custom quote for furnace replacement cost for your home.
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
Furnaces are a whole-home heating solution that work by burning a fuel source, like natural gas or propane, to make heat. The heat produced is combined with cold air from your home, then is re-distributed via ductwork to increase indoor temperature.
A horizontal flow furnace indicates heated air leaves the furnace and enters your ductwork in a horizontal manner so that it can be dispersed through your home. These types of furnaces can be placed on their side.
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.
Dealers can answer questions, help you find the right products for your home, and repair your system.
Connect with our Customer Care team about your products, warranties, and dealer concerns.
Available Monday – Friday from 7am to 5pm CST
A phone