When you’re shopping for a furnace, you’ll see all the specs—BTUs, AFUE ratings, blower types—but one detail many homeowners overlook is just as important: the installation layout.
👉 Should your furnace be installed in an upflow or horizontal position?
The choice matters because it affects airflow, space requirements, maintenance, and even installation cost. When I bought my Goodman 80,000 BTU Ultra-Low NOx Furnace, I had to decide between the two layouts. For me, the answer was upflow—but I’ve seen plenty of cases where horizontal was the better fit.
In this guide, I’ll break down:
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What upflow and horizontal installations mean
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Where each one works best
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The pros and cons of each layout
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Costs, efficiency, and maintenance differences
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My personal experience with both
⚙️ What’s the Difference?
At its core, the installation layout refers to the direction air moves through the furnace and how the furnace is positioned in your home.
🔼 Upflow Furnace
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Air enters the bottom of the furnace.
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Heated air blows upward through the top and into the duct system.
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Typically installed in basements, garages, or closets where ducts run overhead.
↔️ Horizontal Furnace
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Air enters one side of the furnace.
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Heated air exits the opposite side, moving straight across.
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Designed to lie on its side, perfect for attics, crawlspaces, and tight utility areas.
👉 Tony’s Take:
“I think of it like plumbing—you want the airflow to match the direction of your ductwork. If ducts run overhead, upflow is a no-brainer. If they run sideways in an attic or crawlspace, horizontal is the way to go.”
📍 Where Each Layout Works Best
The right layout usually depends on your home’s design.
🏠 Upflow Works Best For:
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Homes with basements or large mechanical rooms.
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Two-story homes with ducts running upward to the main and upper floors.
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Utility closets with enough vertical space.
🏡 Horizontal Works Best For:
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Ranch-style homes without basements.
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Homes with attics or crawlspaces for HVAC equipment.
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Tight installations where vertical clearance is limited.
Energy.gov notes that furnace placement is one of the most important factors in system performance.
🌡️ Comfort and Airflow Differences
Your furnace’s layout impacts comfort more than most people realize.
Upflow Comfort Advantages
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Stronger airflow to upper floors in two-story homes.
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Works well with vertical ductwork layouts.
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Often better at balancing airflow across multiple levels.
Horizontal Comfort Advantages
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Ideal for one-story layouts where ducts run side-to-side.
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Reduces airflow restrictions in attics or crawlspaces.
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Provides efficient heating in homes without basements.
👉 Tony’s Perspective:
“In my two-story house, upflow gave me strong, even heat upstairs and downstairs. But when I helped my brother in his ranch, horizontal was perfect for his attic ducts—no wasted airflow.”
⚡ Efficiency Considerations
The AFUE rating (efficiency) of a furnace doesn’t change based on orientation. An 80 AFUE furnace delivers 80% efficiency whether it’s installed upflow or horizontal.
However, the real-world efficiency can differ depending on installation:
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Poor duct alignment = more leaks and pressure drops.
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Choosing the wrong orientation for your duct layout can force the blower to work harder, wasting energy.
That’s why correct installation is as important as the furnace’s rating.
Energy Star warns that poor installation can cut HVAC efficiency by up to 30%.
💰 Cost Differences
When comparing upflow vs. horizontal, installation cost often makes the difference.
Upflow Costs
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Usually less expensive if you already have a basement and vertical ducts.
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Installers often prefer upflow because of easier access and fewer modifications.
Horizontal Costs
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May be higher if ductwork has to be rerouted to fit the horizontal layout.
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Attic or crawlspace installs sometimes require additional labor (tight spaces, platforms, or condensate management).
👉 Typical Cost Range
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Furnace equipment: $2,000–$4,500 (depending on brand and size).
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Installation labor: $1,500–$3,000.
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Horizontal installs can add $500–$1,000 in labor if ducts need adjustments.
Furnace installation cost guide breaks down averages.
🛠️ Maintenance and Service Access
Don’t forget about serviceability—technicians need space to work on your furnace.
Upflow Maintenance
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Usually easier, with open access in a basement or large closet.
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Easier to reach filters, blowers, and burners.
Horizontal Maintenance
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Trickier if installed in a tight crawlspace or attic.
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Filters may be harder to access.
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Technicians may charge more if access is limited.
👉 Tony’s Perspective:
“I like having my furnace in the basement where I can walk right up to it. When I helped with my brother’s attic unit, crawling around with tools wasn’t fun. It works fine—but keep in mind the long-term service access.”
📊 Pros and Cons Breakdown
✅ Upflow Furnace Pros
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Great for multi-story homes
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Easier maintenance access
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Strong airflow for vertical ducts
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Usually simpler install in basements
❌ Upflow Cons
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Needs vertical clearance
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Not practical for homes without basements
✅ Horizontal Furnace Pros
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Perfect for ranch homes and attics
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Compact design for tight spaces
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Matches side-to-side duct layouts
❌ Horizontal Cons
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Harder to service in crawlspaces
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May increase labor costs for installation
🏗️ Hybrid and Convertible Furnaces
Some furnaces, like Goodman’s, are multi-position:
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Can be installed upflow, downflow, or horizontal, depending on your ductwork.
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This flexibility saves time and money if you remodel or move the furnace later.
👉 Tony’s Tip:
“I went with a Goodman model that supports multiple positions. Even though I installed mine upflow, I like knowing it could go horizontal if I ever move it to the attic.”
Goodman’s multi-position furnace specs show this versatility.
📝 Tony’s Real-World Story
When I upgraded to my Ultra-Low NOx furnace, I had two options:
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Install it upflow in my basement to connect directly to vertical ducts.
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Install it horizontal in my attic (which would have required running new side ducts).
I chose upflow, and here’s why:
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My basement had plenty of space.
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Vertical ducts were already in place.
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It made maintenance easy for me and any technician.
But when I helped my brother with his ranch home, upflow wasn’t an option—he had no basement. His furnace went into the attic horizontally, and it works perfectly for his duct layout.
👉 The lesson? The right choice depends 100% on your home’s design.
🎯 Final Takeaway
The decision between upflow and horizontal furnace installation isn’t about which one is “better”—it’s about which one fits your home.
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Upflow is best if you have a basement or vertical ducts.
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Horizontal is best if your home has an attic, crawlspace, or side ducts.
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Either way, make sure it’s installed properly for maximum comfort and efficiency.
👉 Tony’s Advice:
“Don’t stress over which layout sounds fancier. Look at your house and ductwork. The right orientation is the one that makes your system run smoothly and keeps maintenance simple.
In the next topic we will know more about: Goodman vs. Other Furnace Brands: Why Tony Chose Goodman
