One of the basic principles of physics is that hot air is lighter than cold air and has a tendency to rise. Although this principle seems elementary, it has great bearing when you are looking to buy a new furnace. Home furnaces are available in a diverse range of heating capacities, fuel types, sizes, and shapes. While these aspects are important, one overlooked factor is furnace airflow, so we will explore this topic a little more here.What’s the Difference between an Upflow and Downflow Furnace?

The Air Flow Furnace Basics:

The airflow requirements of your new furnace depends on your present system including the ductwork that distributes the heated air around your home. In simple terms, a furnace installed in the attic will more than likely have ducts running through the walls and ceiling of your home. This format of heating system is usually referred to as a “downflow” furnace. The reason for this is that cool air is drawn in through the top and warm air is pushed out into the ducts through the bottom.
On the other hand, basement furnaces are usually “upflow” systems. They draw in cool air from either the side or bottom and circulate the warm air through the top.

There is another variation of system called a “horizontal” furnace which as you would suspect, draws cool air from one side and pushes out the warmed air from the other. This type of furnace is available as a right to left or left to right configuration; your choice would be determined by the overall layout.

Multi Directional Furnaces:

One of the most popular type of furnace for a new or replacement unit is a multi directional design. These types of furnace allow for the unit to be installed in a downflow, upflow or horizontal position. This creates greater flexibility during installation, which explains their popularity.

Airflow and Efficiency:

Your furnace airflow has no real impact on efficiency. There are no significant efficiency benefits for choosing one type over another. Your choice should be based on the application required by the layout of your home. Generally, it is a good idea to use the same airflow design as your current system when replacing an old furnace. For new installations, it can be preferable to choose a multi directional furnace. Energy efficiency experts agree that one of the best methods to offset increasing energy prices is to replace an old furnace with a more efficient new model. Consumer Reports recommend that you speak to a professional HVAC specialist to help you to determine the correct size and airflow orientation of your new furnace. This will ensure that you benefit from maximum energy efficiency and performance. Cutting corners during installation with an inappropriate size furnace or one with an incorrect airflow orientation will not only affect performance and comfort levels inside your home, but could cost you more in the long run on higher energy bills. You may regret saving a few dollars during installation when you are faced with high energy bills over the next ten, fifteen or even twenty years.