What is HVAC Downflow?

In heating, ventilation, and air conditioning (HVAC) terminology, downflow refers to how the air flows through the furnace or air handler and into your ductwork.  

By Anne Fonda

A downflow gas furnace or air handler takes in cool air at the top and releases warm air down at the bottom. This heated air then circulates through the ductwork system to heat your home.  An attic is the most likely location for a downflow furnace or air handler. In cooling mode, the unit moves cool air in the same way.

An upflow furnace is the opposite of a downflow furnace or air handler in terms of airflow. In an upflow furnace or air handler, the unit draws air in at the bottom of the unit and flows up and out through the top of the unit and into the ductwork. The basement is the most common location for this air handler or furnace installation configuration.

Since heat naturally rises, an upflow furnace is generally more energy efficient than a downflow furnace.  

In a third airflow configuration, the unit lies on its side and the air flows in from one side and out the other side. A horizontal flow furnace or air handler configuration is most common in attics and crawl spaces.

The best HVAC airflow configuration for your home is the one that works best for where you need to install the furnace or air handler. If you need to place the unit in the attic, a downflow configuration would be best. If you have a basement, an upflow model would be best. Finally, if you need to install the furnace or air handler in a crawlspace, a horizontal configuration might be optimal, depending on the height of the crawlspace.

There’s a lot to consider when choosing a new furnace or HVAC system. They include:

A trusted HVAC contractor can help you make an efficient choice and install it in the right location and configuration to work for your type of home and your family.

For more than 100 years, we’ve made some of the most awarded, well-engineered HVAC equipment, and earned a reputation for doing things right. Our furnaces are designed to deliver premium indoor comfort with precise control and come in a range of options to fit each unique application. 

Work with your local American Standard dealer to get a custom quote for furnace replacement with a high-efficiency furnace that will keep your home warm and cozy for years to come.

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