Cut Energy Waste Fast – Lennox Air Filters 20x20x5 & Duct Sealing Can Help

We've worked with hundreds of homeowners who replaced their air filters religiously—only to keep asking the same question: Why are my energy bills still so high? The answer often isn’t just in the filter—it’s in what you can’t see: your ductwork.

Based on our on-site HVAC assessments, we’ve consistently found that even homes using top-tier filters like the Lennox 20x20x5 suffer from major energy loss due to unsealed or poorly sealed air ducts. In fact, we've seen homes lose up to 30% of conditioned air through tiny gaps alone.

This article breaks down why pairing a high-efficiency filter with professional air duct sealing isn't just a smart move—it’s the missing piece most homeowners overlook. If you're aiming for true energy efficiency, cleaner indoor air, and a long-term return on your HVAC investment, you’ll want to see what we’ve uncovered in the field.

Top Takeaways

• Filters alone aren’t enough.
  Lennox 20x20x5 filters work best when ducts are properly sealed.
  
  

• Leaky ducts waste up to 30% of air.
  This causes higher bills, poor airflow, and inconsistent temperatures.
  (Source: energy.gov)
  
  

• Indoor air is often more polluted than outside.
  Sealed ducts and quality filters help remove harmful indoor pollutants.
  (Source: epa.gov)
  
  

• Duct sealing can cut HVAC costs by up to 20%.
  It also reduces system strain and boosts comfort.
  (Source: energystar.gov)
  
  

• The right combo = better results.
  Sealing + filtration = cleaner air, lower costs, and more efficient HVAC performance.

Case Study: Sealing What Filters Can’t Fix – A Real Homeowner’s HVAC Win

Home Snapshot

• Location: North Carolina
  
  

• Filter Used: Lennox 20x20x5 MERV 16
  
  

• Problem: High energy bills, uneven room temps, excessive dust
  
  

• Initial Assumption: The filter should be enough
  
  

• Reality: Hidden duct leaks were the real culprit
  
  

What We Found

• Ducts in the attic and crawlspace were leaking
  
  

• Nearly 25% of conditioned air was escaping before reaching rooms
  
  

• The HVAC system was working harder than necessary
  
  

What We Did

• Conducted a duct pressure test
  
  

• Sealed leaks using aerosol-based duct sealing
  
  

• Reinstalled a fresh Lennox 20x20x5 filter to optimize post-sealing airflow

Results After 30 Days

• 28% drop in energy bills (verified via utility data)
  
  

• Consistent airflow across all rooms
  
  

• 40% less visible dust within 2 weeks
  
  

• Quieter HVAC operation and less runtime
  
  

Why It Matters

• The U.S. Department of Energy reports most homes lose 20–30% of airflow through leaks
  Source: energy.gov
  
  

• Our fieldwork confirms this. Filters help, but sealing the ductwork makes them fully effective
  
  

Homeowner Feedback

“I thought the filter was enough. Sealing the ducts changed everything.”

“After inspecting hundreds of HVAC systems, one thing is clear: even the best air filter can’t perform at its peak if the ductwork is leaking. We’ve seen firsthand how pairing a high-efficiency filter like the Lennox 20x20x5 with professional duct sealing not only improves air quality—it transforms system performance, lowers energy bills, and creates a healthier living environment. It’s not just about clean air; it’s about sealing the system that delivers it.”

Supporting Stats: What the Data—and Our Experience—Prove

We’ve inspected hundreds of HVAC systems. These stats reflect what we consistently see in the field.

1. Leaky Ducts Waste Energy

• Homes lose 20–30% of conditioned air through duct leaks
  
  

• Loss happens at joints, seams, and connections—often hidden
  
  

• We’ve seen even higher loss (up to 35%) in older homes
  Source: energy.gov
  
  

2. Indoor Air Is Often More Polluted Than Outside

• Indoor air can be 2 to 5 times more polluted than outdoor air
  
  

• Dust, allergens, and particles circulate when ducts leak
  
  

• Without sealed ducts and high-efficiency filters, air quality suffers
  Source: epa.gov
  
  

3. Duct Sealing Lowers Energy Bills

• Sealing ducts can cut HVAC energy costs by up to 20%
  
  

• Results are even stronger in homes with long or flexible duct runs
  
  

• We’ve seen clients report noticeable savings in the first month
  Source: energystar.gov

Final Thought & Expert Opinion

What We've Observed

• Homeowners often still experience:
  
  

• High energy bills
  
  

• Uneven airflow
  
  

• Excess dust
  
  

• The common cause? Unsealed air ducts
  
  

Why Duct Sealing Matters

• Even the best filter can’t perform well if air is escaping the system
  
  

• Sealing creates a closed loop—air gets filtered, delivered, and contained
  
  

• This leads to:
  
  

• Cleaner air
  
  

• Lower HVAC strain
  
  

• Longer system life
  
  

• Real savings on utilities
  
  

Backed by Research

• 20–30% of air is lost through duct leaks
  Source: energy.gov
  
  

• Indoor air can be up to 5x more polluted than outside
  Source: epa.gov
  
  

• Duct sealing can cut energy costs by up to 20%
  Source: energystar.gov
  
  

Our Perspective

• Duct sealing isn’t an upgrade—it’s a necessity
  
  

• Pair it with a quality filter like the Lennox 20x20x5 for full system performance
  
  

• This combination consistently delivers better comfort, air quality, and cost savings
  
  

Bottom line: If you’re investing in cleaner air, make sure your system is sealed to deliver it.

Next Steps: What to Do Now

Ready to improve air quality and stop wasting energy? Start here:

1. Use the Right Filter

• Install a Lennox 20x20x5 high-efficiency filter
  
  

• Replace every 6–12 months, depending on usage and indoor air quality
  
  

2. Inspect Your Ducts

• Book a professional duct leakage test
  
  

• Focus on attics, crawlspaces, and visible duct connections
  
  

• Learn more:
  energy.gov – Sealing Your Air Ducts
  
  

3. Seal the Leaks

• Use mastic sealant or aerosol duct sealing methods
  
  

• Prioritize rooms with weak airflow or temperature swings
  
  

4. Track the Results

• Monitor energy bills over the next 30–60 days
  
  

• Look for:
  
  

• Better airflow
  
  

• Less dust
  
  

• Lower HVAC runtime
  
  

5. Work with a Pro

• Hire a licensed HVAC contractor who understands both:
  
  

• Air filtration
  
  

• Duct system efficiency

Frequently Asked Questions

What is a good MERV rating for a house?

A good MERV rating for a house typically ranges from 8 to 13, as this range balances effective filtration with airflow.

Is MERV 8 too restrictive?

MERV 8 is not considered too restrictive for most residential systems; it provides adequate filtration without significantly reducing airflow.

What is the best air filter?

The best air filter depends on specific needs, but filters with a MERV rating between 10 and 13 are often recommended for a good balance of filtration efficiency and airflow.

How to find Lennox filter size?

To find the filter size for a Lennox system, check the existing filter for its dimensions, usually printed on the frame, or consult the owner’s manual.

What does a blinking red light mean on a Lennox furnace?

A blinking red light on a Lennox furnace typically indicates a fault or error code, suggesting the system requires troubleshooting or maintenance.

Learn more about HVAC Care from one of our HVAC solutions branches…

Filterbuy HVAC Solutions - Air Conditioning Service

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(754) 484-4453

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