What to know
Where duct systems actually leak
Not usually along the middle of a run. Leaks happen where two things meet: a joint between sections, the collar where a branch leaves the trunk, the boot under a register, and the connection between flex duct and sheet metal.
Those points were sealed with tape or mastic when the house was built. Tape ages, dries, and lets go. Fittings work loose with years of the system starting and stopping.
Why they get worse over time
A duct system under extra pressure leaks more, and closing registers is the most common way homeowners add pressure without realising. The same is true of a heavily restricted filter.
So a good deal of leak prevention is just not making the system fight itself.
What you can do
- Keep supply and return registers open and unobstructed.
- Change the filter before it is restricting the system rather than after.
- Do not store anything on top of flex duct in an attic or crawl space. It crushes the run and stresses the connections.
- Have a look at accessible runs once a year for tape that has come away or a boot that has pulled loose.
- After any remodelling, check that whoever worked near the ductwork reconnected what they moved.
How to tell you have one
- A room that has quietly fallen behind the rest of the house.
- Noticeably weaker airflow at registers furthest from the furnace.
- An attic or crawl space that feels conditioned when it should not.
- Dust appearing quickly around a register after cleaning, which can indicate air being pulled in on the return side.
What we would do
Look at the accessible ductwork and tell you what condition the connections are in. Sometimes the honest finding is that the system is basically sound and needs cleaning. Sometimes the runs have come apart and cleaning them would be beside the point.
Where duct runs have genuinely lost their integrity, that is a different conversation from cleaning, and we would rather have it plainly than quietly add it to an invoice.