What’s the Difference Between a Downflow vs Upflow Furnace?

When choosing a furnace, you’re probably familiar with factors like fuel type, energy-efficiency ratings, size, and cost. But have you ever stopped to think about the direction your furnace blows heated air? 

The choice between a downflow vs upflow furnace might not seem like a big deal, but the design and installation of your furnace play a big part in the heating system’s efficiency and effectiveness. 

If you’re wondering how these two furnace types differ and why HVAC installers recommend one over the other, HVAC.com breaks down everything you need to know about upflow vs. downflow furnaces.

What Is an Upflow and Downflow Furnace?

The terms “upflow” and “downflow” refer to the direction in which air moves through the furnace and into your home. An upflow furnace takes in cool air from the bottom of the unit, heats it, and pushes the warm air upwards into the ductwork. A downflow furnace draws cool air in from the top, heats it, and sends the warm air downwards into the ducts. This directional difference determines where and how the furnace is installed in your home.

Furnace Upflow vs. Downflow: Key Differences

1. Airflow Direction

The main operational difference between upflow vs downflow furnaces lies in how the air moves:

• Upflow Furnace: Pushes warm air upwards, making it suitable for heating spaces above the installation point.
• Downflow Furnace: Forces warm air downward, which is advantageous for heating spaces located below.

2. Installation Location

The installation location within a home differs for an upflow furnace and downflow furnace:

• Upflow Furnace: This type of furnace is installed in basements or crawl spaces. An upflow furnace works well in homes where the ductwork is located above the furnace.
• Downflow Furnace: These are ideal for homes with attics or installations on the main floor, where the ductwork is below the furnace.

3. Energy Efficiency

Both furnace types can be energy efficient if properly matched to the home’s layout. However:

• Upflow Furnaces: May perform better in cooler climates since heat naturally rises, complementing the furnace’s airflow direction.
• Downflow Furnaces: Are well-suited to warm climates but might require additional insulation in cooler areas to prevent heat loss through the floor.

4. Comfort and Distribution

The airflow direction of your furnace impacts comfort and heat distribution in the home:

• Upflow Furnace: Provides even heat distribution in multi-story homes by pushing warm air upward to fill the higher floors.
• Downflow Furnace: Offers efficient heating in single-story homes by directing heat straight into the lower ducts.

Why HVAC Installers Choose a Downflow or Upflow Furnace

HVAC professionals consider several factors when determining whether an upflow furnace vs downflow furnace is right for your home:

Climate

Colder climates favor upflow furnaces because the upward movement of heated air helps combat the chill. Conversely, warmer climates often use downflow furnaces to maximize cooling efficiency and optimize heating.

Installation Space

If space is limited or unconventional, the installer might choose a furnace type that best fits the area. Basements lend themselves to upflow furnaces, while attics or closets often house downflow units.

Advantages and Disadvantages of Upflow vs. Downflow Furnaces

Upflow Furnace Pros:

• Ideal for colder climates.
• Helps evenly heat multi-story homes.
• Easy to maintain in basement installations.

Upflow Furnace Cons:

• Requires more vertical space for installation.
• Less effective if ductwork is not properly insulated.

Downflow Furnace Pros:

• Great for homes without basements.
• Works well in warm climates.
• Fits in compact spaces like attics.

Downflow Furnace Cons:

• May cause heat loss if flooring isn’t insulated.
• Can be less efficient in colder climates.