HVAC 101: The Installation Position

This is the first blog in a series explaining the basics of heating and cooling with a forced air system. This series will look at the different parts including the installation, the furnace, the air conditioning unit, the duct work, the thermostat and indoor air quality. I will hopefully explain how the parts and pieces work to deliver the maximum comfort for you inside your home.Furnaces are installed in one of three positions, up-flow which is the most common in the Chicagoland area, down-flow and horizontal. No heating and cooling system will function properly if it is not installed properly.


Air comes into the furnace through the return duct work in the side or the bottom of the furnace and is then pushed upward past and through the heat exchanger where it is heated and delivered through the supply ductwork throughout the house. Most up-flow furnaces are installed in the basement of a house.


In a down-flow installation, the air comes into the furnace from the top through the return ductwork and is then pushed downward through the heat exchanger and then delivered through the supply ductwork.  Most down-flow installations occur in homes built over a crawlspace or in homes built on concrete slabs.


A horizontal furnace is nothing more than a down-flow installation turned on its side. The air flows from one side, is heated and then delivered through the house via the supply ductwork. Most commonly a horizontal installation is required when the furnace is located in the crawlspace or in an attic.

The installation position will ultimately depend on your home and your duct system. All three installations, when done properly, can deliver maximum comfort and the best indoor air quality.

One thought on “HVAC 101: The Installation Position

  1. Pingback: HVAC 101: The Furnace | I Heat Chicago! I Cool Chicago!

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