(By Tony the Trusted Tech)
Let me ask you something: You just spent thousands on a new high-efficiency HVAC system, like a 14.5 SEER2 Goodman R-32 setup. But the house still has hot spots, your bills are creeping up, and the unit seems to short-cycle. What gives?
Here’s the dirty truth no one puts on the product label:
SEER2 only tells you the potential. If your ductwork is trash, you’re not getting anywhere near that number.
I’ve worked on hundreds of systems that underperform right out of the box—not because the equipment was bad, but because the duct design was garbage or the airflow was never dialed in.
Let’s break this down the way contractors, landlords, and DIYers can actually use.
1. What SEER2 Actually Measures (and What It Doesn’t)
SEER2—short for Seasonal Energy Efficiency Ratio 2—is the latest testing standard used by the DOE to simulate real-world system performance. It’s more accurate than old SEER numbers because it adds external static pressure to the test, reflecting real duct resistance.
But here’s the catch:
The rating assumes a properly sized, properly installed, fully compatible duct system.
And we all know that’s rare.
So even if you buy a 14.5 SEER2-rated condenser, like the Goodman GLXS4BA3610, and pair it with the matching handler, poor airflow will tank your performance.
To understand how much duct design matters, check out this Department of Energy guide on HVAC efficiency and duct leakage.
2. Undersized Ducts: The Silent Killer
This is the #1 airflow mistake I see: installers reuse old 6" or 7" duct trunks that were never meant to handle modern airflow needs.
Here’s why that’s a problem:
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Undersized ducts choke airflow
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It causes high static pressure
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Your blower motor works harder (and can burn out)
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Your cooling coil freezes, leading to water damage and short cycling
Use a ductulator or static pressure chart to verify your duct sizes against your air handler’s rated CFM. For a 3-ton system, you’re looking at 1,200 CFM minimum.
For pros, the Air Conditioning Contractors of America (ACCA) Manual D is the gold standard in duct design.
3. Leaky Ducts Are Just as Bad
Even if your ducts are sized right, leaks will rob you blind. According to ENERGY STAR, the average home loses 20%–30% of conditioned air through leaky ducts.
That means your 14.5 SEER2 system might be operating like an 11 or 12 SEER in the real world. Not great.
Here’s how to spot duct leaks:
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Whistling or hissing sounds
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Hot rooms far from the air handler
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Dirt streaks around joints and vents
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High static pressure on a manometer test
Seal with mastic, not duct tape (the irony, right?), and consider duct leakage testing for any system replacement job.
4. Return Air: The Most Ignored Part of the System
Everyone focuses on supply ducts, but return air is just as important. Without adequate return, your blower pulls a vacuum, causing:
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Whistling doors
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Reduced cooling
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Poor humidity removal
General rule of thumb: You need 1 square inch of return grille per CFM of airflow.
For a 3-ton system:
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1,200 CFM = 1,200 sq in of return grille
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That’s roughly (2) 20x30 grilles or (3) 16x25s
You’d be surprised how many homes are trying to breathe through a single undersized hallway return. It’s like running a marathon with a straw.
5. Air Balancing and Register Placement
Even perfect ducts can fail if airflow isn’t balanced. I’ve seen rooms with two vents blowing like a hurricane and others with barely a whisper.
Quick tips:
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Supply vents should blow toward the exterior walls
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Returns should be placed high on walls or low in hallways
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Use manual dampers to balance airflow — don’t rely on register covers alone
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Avoid placing vents behind doors or furniture
6. Total External Static Pressure (TESP): Your System’s Blood Pressure
If your TESP is too high, your system is fighting itself. High pressure = low airflow.
Most manufacturers want:
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0.5" WC or less (water column)
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Some ECM blowers can handle up to 0.8" WC, but you’ll lose efficiency
Use a manometer to measure pressure across the filter, coil, and duct system. If it’s too high:
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Check for dirty filters or coils
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Look for undersized ducts
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Make sure flex duct runs are short and not kinked
Check out Fieldpiece’s guide to TESP testing for a deep dive.
7. What to Ask Before Replacing Your System
Before you drop a few grand on a new system—R-32 or otherwise—ask your contractor:
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Have you done a Manual D duct calculation?
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Will you measure static pressure and CFM after install?
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Are the ducts sealed and insulated properly?
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Can I see the AHRI match certificate for this setup?
If they give you a blank stare or try to sell you “rule of thumb sizing,” run.
Final Thought: Your Ductwork Is Part of the System, Not an Afterthought
You wouldn’t buy a Ferrari and put lawnmower tires on it, right?
So don’t install a high-efficiency 14.5 SEER2 R-32 system and let a leaky, undersized duct system kill the performance.
Efficiency isn’t just about ratings — it’s about execution.
Tony’s Pro Tip:
You can have a 14.5 SEER2 rating on paper, but if your system’s pulling 0.9" static and you’ve got 30% duct leakage? You’re probably getting the equivalent of a 10 SEER performance. That’s a whole tier lower.
Watch out for our next article on "Should You Retrofit an Old R-410A System with R-32? What Tony Thinks"
