How long does ductwork last?
InterNACHI's baseline chart gives household ducting 60 to 100 years, one of the longest figures anywhere on it. The 2007 NAHB survey chart, built from the same kind of industry phone calls, prints a flat 10. Nobody warrants the ducts in your house at all — they were never a product, they were cut, hung and sealed in place on site.
Updated
Typical service life: 60–100 years
The 60-to-100 figure is InterNACHI's single "Ducting" line, and it does not split by material. The other common baseline disagrees sharply: NAHB's 2007 survey chart prints a flat 10 years for ducting. The Air Duct Council, the trade body for flexible duct makers, answers the same question about its own product with "flexible air ducts should last for the life of the dwelling" when installed to the instructions in the shipping carton. Three published answers, three different pictures — which is the honest state of the evidence for something that is never sold as a finished object.
Tier 3 · baseline chart (undated) Range from InterNACHI — Standard Estimated Life Expectancy Chart for Homes, checked 2026-08-27.
Where the duct lives decides most of this. A steel trunk in conditioned basement air sits at room temperature its whole life and can plausibly reach the top of the chart's range. The same house's flexible branches in a vented attic swing through the full annual temperature range every year, and in a humid climate the outside of the jacket sweats every time the cooling runs hard. Fibrous glass duct board is a third case again: dry, it is stable and quiet; wet, it has no good outcome, which is why the trades treat any water reaching it as a different kind of problem from water reaching sheet metal.
Why there is no warranty bar here
Ductwork in a house is not a product with a warranty; it is site work. The sheet metal was cut and hung, the flexible duct was pulled and strapped, the fibrous glass board was scored and taped by whoever was on the job that week. What governs is the installer's own workmanship guarantee, if there was one, and the fabrication and installation literature the trades work to — SMACNA's duct construction standards, ACCA's residential manuals, the Air Duct Council's installation instructions that ship in the carton with flexible duct. Individual components each carry their own paper: a roll of flex, a pail of mastic, a sheet of duct board. The assembly above your ceiling does not, and no manufacturer has ever offered one for it.
What shortens it
- Crushed, kinked or sharply bent flexible duct, which stays crushed for the rest of its life
- Long unsupported runs of flex sagging between straps, so the inner liner rides in loops the air has to fight through
- Attic and crawl-space temperature swings working the outer jacket and the tape at every joint, twice a year, for decades
- Direct sunlight through a gable vent or an open soffit — the Air Duct Council's own guidance is to shield both the outer vapor barrier and the inner core from UV unless the product is made to take it
- Rodents and pests in an attic or crawl space, which open the jacket and then the liner
- Tape used where mastic belongs: the joints, not the duct body, are what usually let go first
Signs of wear to look for
- Rooms at the end of a run that never quite catch up with the rest of the house, in either season
- Visible sag, kinks or crushed sections wherever duct is reachable in a basement, attic or crawl space
- Torn or hanging outer jacket on flexible duct, or insulation gone loose around the core
- Grey dust streaks fanning out on the ceiling or wall around a register, which track air escaping at the boot
- Joints where the tape has curled, browned or fallen off, leaving the connection standing open
- Registers that whistle or roar at high fan speed on runs that used to be quiet
Duct that has been wet, or that runs through a space where something has been leaking, is not a thing to judge from a photograph or a page — that is an inspection question, not a web-page question.