Home & Appliances

How Long Do Air Ducts Last?

Air duct systems last 15–25 years. Leaky ducts are one of the most common causes of high energy bills — up to 30% of conditioned air escapes through unsealed joints.

15–25 years

Quick Facts

Average Lifespan

15–25 years

Replacement Cost

$2,500–$4,500

Source

InterNACHI

Overview

Duct systems are one of the most invisible and misunderstood components of a home. InterNACHI data shows duct systems lasting 15–25 years, but the failure mode is rarely dramatic — ducts develop small leaks and disconnections over time that gradually reduce HVAC efficiency without obvious symptoms. The US Department of Energy estimates that the typical home loses 20–30% of conditioned air through duct leaks before it reaches the intended rooms. Flexible (flex) ductwork installed between the 1970s and 1990s often contains issues earlier than rigid metal duct systems.

Signs It Is Time to Replace

Rooms that are consistently harder to heat or cool than others
HVAC system running longer than it used to reach set temperature
Higher than expected energy bills without changes in usage
Dusty supply registers even with frequent filter changes
Musty odors from vents — potential mold growth in ductwork
Age over 20 years for flex duct systems
Visible gaps, tears, or disconnections in accessible ductwork (attic, crawlspace)

How to Make It Last Longer

Have ducts professionally inspected and pressure-tested every 5 years
Seal accessible duct joints with mastic sealant or metal tape (not regular duct tape — it fails quickly)
Ensure all supply and return registers are open and unobstructed
Add insulation around ducts in unconditioned spaces (attic, crawlspace)
Duct cleaning is rarely necessary unless the system has been contaminated — skip the upsell

What Affects Replacement Cost

Material type — flex duct replacement vs. rigid sheet metal
Accessibility — attic and crawlspace work adds labor cost
Extent of work — sealing leaks vs. partial replacement vs. full replacement
Whether the system needs to be rebalanced after duct work

When to Replace

Replace ductwork when pressure testing shows significant leakage that sealing cannot address, when flex ductwork is over 20 years old and showing deterioration, or when you are replacing the HVAC unit (replacing ducts at the same time is far more cost-effective than separately). Many older homes benefit enormously from duct sealing alone — a $500–$1,500 professional sealing job can reduce HVAC energy use by 20–30%.

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Pro Tip

Aeroseal duct sealing is a professional service where sealant particles are blown through the duct system and adhere to leak points from the inside. It can seal ducts that are inaccessible for manual sealing (in walls or floors) and typically reduces duct leakage by 70–90%. If your HVAC system runs constantly but doesn't reach set temperature, Aeroseal is worth the $1,500–$3,000 investment before replacing the entire duct system.

Frequently Asked Questions

How often should air ducts be cleaned?+

The EPA says duct cleaning is rarely necessary for most homes and should only be done if ducts are visibly contaminated with mold, contain large quantities of debris from renovation work, or harbor pest infestation. The "duct cleaning services" industry frequently oversells the need. Regular filter changes do more for air quality than duct cleaning.