How To Seal Leaky Ductwork

Sealing leaky ductwork will help maintain an energy-efficient home. Many homeowners overlook this important task, but addressing duct leaks can significantly improve your heating and cooling system’s performance while reducing energy bills. In the video, This Old House expert Richard Trethewey demonstrates an innovative method for sealing ductwork from the inside, providing a comprehensive solution to this common household issue.

Understanding Duct Leakage

Duct leakage is a widespread problem that can lead to significant energy waste and reduced comfort in your home. When ducts leak, conditioned air escapes before reaching its intended destination, forcing your HVAC system to work harder and consume more energy.

Common Causes of Duct Leaks

Several factors can contribute to leaky ductwork:

• Poor installation or connections
• Age-related wear and tear
• Damage from pests or accidental impacts
• Improper sealing during initial installation

Impact of Leaky Ducts

Leaky ducts can have several negative consequences:

• Increased energy bills due to wasted heating and cooling
• Inconsistent temperatures throughout the house
• Poor indoor air quality from dust and pollutants entering the system
• Reduced overall HVAC system efficiency

Traditional Methods for Sealing Ductwork

Before exploring newer technologies, it’s important to understand the conventional approach to duct sealing. This method involves manually sealing visible duct sections, which can be effective but has limitations.

Materials Needed

To seal ductwork using traditional methods, you’ll need:

• Foil tape (not duct tape)
• Duct mastic
• Fiberglass insulation
• Utility knife
• Paintbrush

Step-By-Step Process

Sealing ducts traditionally involves a straightforward yet labor-intensive process:

1. Use foil tape to seal longitudinal seams along straight duct runs.
2. Apply duct mastic with a paintbrush to joints where elbows connect to ducts.
3. Measure and cut fiberglass insulation to fit around the ducts.
4. Wrap insulation around the ducts, securing it with foil tape.
5. Apply a long strip of foil tape along the insulation seam.
6. Repeat the process for all accessible ductwork.

While this method can be effective for visible ducts, it doesn’t address leaks in hidden or inaccessible areas of your ductwork system.

Advanced Duct Sealing Technology

Trethewey introduces an innovative approach to duct sealing that addresses the limitations of traditional methods. This technology seals ducts from the inside, reaching areas that are typically inaccessible.

How It Works

The advanced sealing process involves the following steps:

1. Sealing all supply and return registers to isolate the duct system.
2. Pressurizing the duct system using a specialized fan.
3. Injecting a liquid sealant into the pressurized ducts as an aerosol.
4. Allowing the sealant particles to accumulate at leak points, effectively sealing them from the inside.

This inside-out approach ensures that even hidden leaks are effectively sealed.

Benefits of Inside-Out Sealing

This method offers several advantages over traditional duct sealing:

• Reaches all areas of the duct system, including hidden sections
• Provides a more comprehensive seal
• Reduces the need for destructive access to walls or ceilings
• Offers measurable results through pre- and post-sealing tests

Additionally, this method ensures that your HVAC system operates more efficiently, which can lead to long-term cost savings and improved comfort.

Preparing for Sealing Leaky Ductwork

Before beginning any duct sealing process, it’s essential to properly prepare your HVAC system and home.

System Inspection

Conduct a thorough inspection of your ductwork and HVAC system:

• Check for visible damage or disconnections
• Listen for any unusual noises during system operation
• Look for signs of excessive dust around vents or returns

Identifying these issues beforehand will help ensure a more effective sealing process.

Cleaning and Maintenance

Ensure your system is clean and well-maintained by regularly changing or cleaning air filters and removing any debris from vents and returns. Schedule a professional HVAC maintenance check if needed. Routine maintenance can significantly improve the efficiency and lifespan of your system.

Professional vs. DIY Duct Sealing

While some homeowners may be tempted to tackle duct sealing as a DIY project, there are important considerations to keep in mind when deciding between professional and DIY approaches.

When To Call a Professional

Consider hiring a professional for duct sealing if:

• You have limited access to your ductwork
• Your home has a complex HVAC system
• You want to use advanced sealing technologies
• You lack the necessary tools or expertise

Professionals have the equipment and knowledge to ensure that all areas of your duct system are properly sealed.

DIY Duct Sealing Tips

If you choose to seal your ducts yourself, follow these tips:

• Focus on accessible areas like attics and basements
• Use appropriate materials (foil tape and mastic, not duct tape)
• Be thorough in your application of sealants
• Consider renting a blower door for testing

While DIY sealing can address many common issues, remember that it might not be as comprehensive as a professional service.

Gauging Duct Sealing Effectiveness

It’s important to measure the effectiveness of your duct sealing efforts to ensure their success. Trethewey demonstrates how professionals use specialized equipment to quantify duct leakage before and after sealing.

Pre-Sealing Test

Before sealing, a baseline measurement is taken:

• The duct system is pressurized
• Airflow is measured to determine the extent of leakage
• Results are typically expressed in cubic feet per minute (CFM)

This initial test helps identify the severity of the leaks and provides a benchmark for comparison.

Post-Sealing Evaluation

After sealing, the test is repeated to measure improvement:

• The system is pressurized again
• New airflow measurements are taken
• Results are compared to pre-sealing numbers to calculate the reduction in leakage

In the demonstration, the system showed a remarkable 94% reduction in duct leakage after the advanced sealing process. This significant reduction indicates a vastly improved HVAC efficiency.

Additional Benefits of Proper Duct Sealing

Beyond energy efficiency, sealing your ductwork offers several other advantages that contribute to a more comfortable and healthier home environment.

Improved Indoor Air Quality

Sealed ducts prevent the infiltration of dust, allergens, and other pollutants. This can reduce the amount of airborne particles in your home and help maintain a cleaner living environment. This is particularly important if you’re hoping to alleviate symptoms for allergy and asthma sufferers.

Enhanced HVAC System Longevity

By reducing strain on your heating and cooling equipment, sealed ducts can extend the lifespan of your HVAC system, decrease the frequency of repairs, and improve overall system performance. A well-maintained system will save you money in the long run.

Increased Home Comfort

Properly sealed ducts contribute to more consistent temperatures throughout your home. You’ll enjoy the elimination of hot and cold spots, improved airflow to all rooms, and a reduction of the need to adjust thermostat settings frequently. Consistent temperatures improve overall comfort and reduce the demand on your HVAC system.

Cost Considerations of Sealing Leaky Ductwork

Investing in duct sealing can have varying costs, depending on the method and whether you hire a professional or opt for a DIY approach.

Professional Sealing Costs

Professional duct sealing services can range in price:

• Inside-out sealing technology typically costs between $0.50–$1.50* per square foot of ductwork.
• Traditional methods might be less expensive initially but can miss hidden leaks.

Getting a professional evaluation will help you understand the best option for your home.

*Cost data in this article sourced from contractor estimates used by Angi.

Our Conclusion

Sealing leaky ductwork is an important step in optimizing your home’s energy efficiency and comfort. While traditional methods can be effective for accessible areas, advanced technologies like the one demonstrated by Trethewey offer a comprehensive solution for entire duct systems. Whether you choose a DIY approach or hire a professional, addressing duct leaks can lead to significant improvements in your home’s heating and cooling performance.