🔧 Introduction: Furnace Positioning Is Airflow Positioning — Not Just “Where It Fits”
Most installers place a furnace wherever it physically fits:
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in a corner,
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in a closet,
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against a wall,
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near the water heater,
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beside the electrical panel,
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or in whatever space the homeowner clears out.
But that’s not how houses breathe.
Furnace position should be based on airflow geometry, not convenience.
80,000 BTU 96% AFUE Upflow/Horizontal Single Stage Goodman Gas Furnace - GR9S960803BN
I’ve seen beautifully sized equipment perform terribly simply because the furnace was shoved into a spot that made sense for plumbing—but not for air.
My field formula solves this.
This is how I determine the exact placement of a furnace so it aligns with a home’s natural airflow patterns, ensuring:
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low static pressure
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proper return mixing
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balanced supply distribution
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stable temperature rise
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minimal noise
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long blower life
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even comfort across floors and rooms
Let’s break down the science, the field rules, and the step-by-step method.
🧭 1. How Homes Actually Move Air (The Part 90% of Installers Forget)
Air doesn’t move because of duct size alone.
Air moves because of:
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pressure differentials
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natural convection patterns
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building layout
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door and hallway geometry
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floor-to-floor temperature shifts
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stack effect
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return air proximity
External verified link:
• Building Science Corporation – Airflow & Pressure Basics
https://www.buildingscience.com
When you install a furnace without considering these forces, you end up with:
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cold bedrooms
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overheated basements
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loud blowers
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coil freeze-ups
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return starvation
To position a furnace properly, you must understand how the home wants to breathe.
🏠 2. Jake’s Rule: The Furnace Must Sit Where the Air Naturally Equalizes
Every home has a “pressure-neutral zone.”
This is the point where:
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supply air can branch efficiently,
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return air can re-enter without turbulence,
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and the blower does not fight against the duct system.
When the furnace sits too far off that zone, the system becomes:
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noisy,
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uneven,
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high static,
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inefficient.
Jake’s Rule:
Place the furnace as close as possible to the return trunk’s gravitational center of the home.
This ensures air circulates evenly—even before the blower kicks in.
📏 3. The 5 Measurements Jake Takes Before Choosing Furnace Location
Before I even move the old furnace out, I measure:
1️⃣ Return Drop Location
Where does the main return trunk enter?
2️⃣ Supply Trunk Orientation
Is the supply trunk centered, offset, or broken into multiple runs?
3️⃣ Home Geometry
Where are:
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load-demand rooms?
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long duct runs?
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second-floor supplies?
4️⃣ Plenum Height & Transitions
Does positioning the furnace here allow a tall, quiet plenum?
5️⃣ Natural Airflow Path
How does air move room-to-room without mechanical force?
If anything feels “fought,” the furnace location needs adjusting.
⚙️ 4. The Three Furnace Positions — And What They Mean for Airflow
Homes typically allow one of these furnace placements:
🟥 1. Central Position (Ideal)
Furnace sits near the center of the supply and return geometry.
Benefits:
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lowest static
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best temperature consistency
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quietest blower
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lowest energy usage
Common in:
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full basements
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split-level homes
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ranch homes with central mechanical rooms
🟦 2. Offset Position (Acceptable with Modifications)
Furnace sits off to one side of the home.
Requires:
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return enhancement
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longer transitions
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balancing dampers
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additional return grille(s)
Common in:
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older homes
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tight utility rooms
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crawlspaces
🟩 3. Perimeter Position (Worst for Airflow)
Furnace is installed on a side wall or corner of the basement.
Risks:
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long duct runs
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uneven airflow
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noisy blower
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hot/cold spots
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higher static pressure
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poor return mixing
Only acceptable if:
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return is oversized
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supply is redesigned
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coil and plenum transitions are optimized
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additional returns are added
🌡️ 5. Jake’s Airflow Triangle: Furnace → Coil → Return Drop
A furnace isn’t a standalone appliance—it’s part of a triangle:
🔼 1. Furnace
Source of movement.
🔽 2. Coil
Creates resistance.
🔽 3. Return Drop
Allows the blower to breathe.
If any leg of the triangle is out of alignment, you get:
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rumble
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whistle
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high static
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freeze-ups
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blower strain
To maintain harmony, Jake ensures:
✔ Furnace aligns perfectly with the return drop
✔ Coil sits centered on the furnace
✔ Plenum rises straight above the coil
✔ No sharp elbows directly off the furnace
This geometry is what makes airflow stable.
📐 6. Jake’s Positioning Formula (The Field Math)
Here is the formula I use in the field:
Furnace center = (Return trunk center + Supply trunk center) / 2
This puts the furnace in the neutral pressure zone.
More detailed:
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Find the return trunk midpoint
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Find the supply trunk midpoint
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Average those points
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Move furnace to that center point
This instantly drops total static pressure by 0.05–0.15” WC.
And if you know static, you know that’s massive.
📦 7. The Return Air Side Must Dictate Furnace Position
Most installers position furnaces based on:
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gas line
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electrical panel
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drain location
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existing venting
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clearance to the wall
Wrong approach.
The furnace should be positioned to optimize return airflow, then everything else adapts.
Jake’s Rule:
The furnace must sit where the return air enters most cleanly and evenly.
This ensures the blower wheel sees uniform airflow, reducing:
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turbulence
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noise
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coil face imbalance
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static pressure
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blower wattage
External verified link:
• Energy Star HVAC Installation Best Practices
https://www.energystar.gov
🔊 8. Avoid These Positioning Mistakes (They Create Noisy Systems)
❌ Furnace pushed into a corner
Air cannot approach the return evenly.
❌ Furnace turned sideways to “make it fit”
Return becomes high static.
❌ Coil off-center from supply trunk
Turbulent airflow → blower howl.
❌ Furnace too far from return drop
Creates a vacuum effect.
❌ Elbowed immediately at the furnace outlet
No room for expansion → turbulence.
❌ Furnace installed under low joists
Prevents tall plenum → higher static.
❌ Ignoring floor plan geometry
Second floors get starved instantly.
Most noise issues begin with poor positioning.
🧰 9. Jake’s Step-by-Step Positioning Method
This is the exact 10-step method I use on every install.
🟦 STEP 1 — Identify the house’s natural airflow “spine”
This is the path running roughly through the center of:
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main hallway
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stairwell
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open-plan space
🟧 STEP 2 — Locate the return trunk’s centerline
Take actual measurements.
🟩 STEP 3 — Identify the supply trunk distribution center
Find the midpoint of all major supply runs.
🟥 STEP 4 — Calculate the neutral furnace position
Use the Airflow Center Formula:
(Return center + Supply center) / 2
🟪 STEP 5 — Position furnace so return air hits squarely
Do not let return air enter at an angle.
🟫 STEP 6 — Confirm coil can sit centered on furnace
Check vertical and horizontal alignment.
🟨 STEP 7 — Ensure room for a tall, quiet plenum
The first 12–18" above the coil MUST be straight.
⬛ STEP 8 — Check for obstructions (gas, water, venting)
Move utilities if necessary.
⬜ STEP 9 — Confirm service clearances and code requirements
NEVER sacrifice airflow for convenience.
External verified link:
• International Mechanical Code Clearances
https://codes.iccsafe.org
🟦 STEP 10 — Anchor the furnace in the neutral position
Use Jake’s Two-Point Anchor Rule to prevent movement and vibration.
🔄 10. Furnace Position vs. Temperature Consistency (The Missing Link)
Homes with uncomfortable temperature differences between:
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upstairs vs. downstairs
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bedrooms vs. living room
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front vs. back
…almost ALWAYS suffer from furnace mispositioning.
Proper furnace placement:
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stabilizes pressure zones
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improves return mixing
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reduces duct losses
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makes airflow predictable
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balances room-to-room temperature
Positioning is not cosmetic—it is comfort engineering.
🧪 11. Jake’s Post-Positioning Verification Tests
After setting the furnace, I run three tests before I hook up a single duct:
✔ 1. Static Prediction Test
Using return + supply geometry, predict total static.
Target: < 0.50" WC
✔ 2. Natural Draft Behavior Test
Open basement door and observe mini air currents.
If the furnace sits in a stagnation pocket, move it.
✔ 3. Lighting and Access Simulation
Can you:
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reach the gas valve?
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remove the blower?
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pull the coil?
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remove both doors?
Airflow must not come at the expense of serviceability.
📘 Conclusion: Furnace Positioning Is the Foundation of a High-Performance System
Anyone can install a furnace.
But only professionals understand how furnace positioning controls:
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airflow
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pressure
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noise
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temperature balance
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blower longevity
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coil performance
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efficiency
Jake’s Field Formula ensures the furnace sits exactly where the home wants it to be—not where convenience puts it.
This is how you:
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produce quiet systems
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deliver even comfort
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lower static
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prevent freeze-ups
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eliminate blower strain
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reduce energy usage
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create long-lasting installs
Furnace positioning is airflow positioning.
Position it right, and the home breathes perfectly.
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In the next topic we will know more about: Cabinet Perfection: Jake’s Method for Positioning a 17.5-Inch Goodman Furnace in Tight Utility Spaces
