Duct Leakage 101: What is Duct Leakage?
In a previous post, we explained the differences between ductwork (one word) and duct work (two words). Here’s a summary:
- Ductwork is used to reference a set of air ducts in a home or building
- Duct work is work performed on air ducts.
You cannot talk about ductwork or duct work without talking about duct leakage.
It’s a significant and often overlooked aspect of homes and buildings that causes issues associated with heating, ventilation, and air conditioning (HVAC) systems.
Duct leakage is when conditioned air gets distributed from a SEER AC unit or AFUE furnace and leaks through holes/cracks/seams in the ductwork (a.k.a. air ducts) before it reaches the desired rooms/spaces in a home or building. According to ASHRAE (industry authority for HVAC stuff), 75% of buildings have duct leakage. Furthermore, the majority of homes leak on average 10-25% conditioned air!
There’s also different types of duct leakage. The Journal for Light Construction (JLC) outlines them in a nice article:
- Supply Leakage: When supply air ducts leak, airflow from the AC unit or furnace to the desired rooms/spaces is decreased.
- Equipment Leakage: This leakage can often be the most overlooked. HVAC equipment components like coil cabinets and furnace cabinets all have “seams” that either suck or blow air. If those small pieces of the equipment are not sealed, then airflow is also decreased.
- Return Leakage: When return air ducts leak, unconditioned air from unconditioned spaces like attics and wall cavities gets sucked into the ventilation system and distributed back to the equipment. This added load creates more work for your HVAC equipment. Instead of simply reconditioning air, it’s conditioning air from unconditioned spaces.
For more information about these different types of duct leakage, read the full JLC article.
Duct Leakage Causes Common HVAC Issues
Since air is obviously invisible, many homeowners and building owners don’t realize duct leakage causes common HVAC issues:
- Hot/cold spots in rooms
- Excessive dust, dirt, and airborne allergens
- High energy/utility bills for heating and cooling
To identify duct leakage, HVAC contractors can use infrared technology to make invisible air visible. Then you can actually see duct leakage!
Here’s a brief video that shows the benefits of sealing ductwork in homes (and buildings too):
Are you a homeowner? Make your home more comfortable and efficient with proper duct performance. Find an Aeroseal dealer near you to learn more about the different types of duct work and how to get started.
Want to Learn More? Ask the HVAC Expert
About Ken Summers
Ken Summers has more than 30 years of experience in the HVAC industry. Starting in 1980, he did residential service, in-home sales, and commercial design/build. In 1995, he joined Retrotec, a manufacturer of test instruments used in performance contracting such as blower doors and duct air tightness testers, where he trained contractors how to use test instruments to understand better on how houses worked from a comfort and indoor air quality (IAQ) basis. In 1998, he co-founded Comfort Institute (CI), a leading home performance training organization. For the past 20+ years, he has been with CI helping progressive HVAC contractors adopt whole-house and air distribution system diagnostics and repair. In 2014, CI joined Aeroseal where Ken is the Vice President of Training. Ken specializes in helping contractors avoid common issues related to HVAC load calculation and duct design mistakes, duct leakage problems, thermal envelope repair, and mold related issues across the country. He has spoken at many industry leading events including ACCA, PHCC, RSES, EPA, EGI as well as being brought in to speak with local utility and code officials across the country about how the house works as an interactive system.