Duct Sealing and Duct Leakage Testing in Antioch, CA
Duct leakage testing and sealing for Title 24
Leaky ducts are one of the most common reasons a house in East County never quite cools down. Most ducts here run through hot attics, so every gap at a boot, plenum or joint either leaks cooled air into the attic or pulls hot attic air in. We find those leaks, seal them with mastic and code-rated tape, and check the result. When you replace a furnace, AC or heat pump, California's Title 24 code usually requires a duct test anyway, so sealing and replacement often happen together.
Why choose Blue Star
Blue Star has held CSLB license #880647 (C-20) since 2006, and duct work has always been part of what we do: repairing, redesigning and replacing duct systems in homes, apartments and commercial buildings. On a change-out, we seal the ducts before the third-party ECC rater (formerly called HERS) arrives, so the test isn't a surprise. We take pictures of what we find so you can see it, and your written quote covers the work. We'd rather fix the leak than sell you a bigger system.
- Leak check before we seal
- Boots and plenums sealed
- Mastic and UL 181 tape
- Crushed or loose runs fixed
- Ready for the ECC rater
- Photos of what we found
Where we work
Most tract homes in Southeast Antioch, Oakley and Brentwood were built in the 1990s and 2000s with flex duct in the attic, and on a 100 degree afternoon that attic gets far hotter than the yard. North Antioch homes date mostly to the 1970s, and Concord, Pleasant Hill and Lafayette are older still, often with crawlspace ducts and decades of patched joints. Bay Point, Discovery Bay, Byron, Knightsen and Bethel Island permit through Contra Costa County, whose permits note that an ECC report may be required at final.
Major corridors
- SR-4
- SR-160
- Lone Tree Way
- Deer Valley Rd
- Somersville Rd
- SR-242
- Ygnacio Valley Rd
- I-680
We do this across our service area:
Each link opens that town's heating and air page.
4.9 stars on Google
Read more reviewsColton was great. He found the problem right away and did a temporary fix to get my a/c running until he could get the right part ordered. He also made sure every inside was working well.
Questions we hear
Is duct testing required when I replace my AC or furnace?
In most cases, yes. Under California's Title 24 Energy Code, replacing a furnace, air conditioner or heat pump needs a permit and, for most systems, field verification by a third-party ECC rater (the 2025 code's name for a HERS rater). When the indoor or outdoor unit of a split system is replaced, the existing ducts generally have to be tested and sealed. The exact requirements depend on what you replace and where the ducts run.
What leakage number do my ducts have to hit?
For existing ducts on a change-out, the usual targets are 10% or less total leakage, or 7% or less leakage to the outside. When ducts can't reasonably reach those numbers, the code allows alternatives such as a smoke test or sealing all accessible ducts. The ECC rater runs the official test. We seal beforehand so your ducts are ready, and if a run fails, we fix it and the rater retests.
Why can't the installer do the official test?
Title 24 requires the verification to come from an independent, state-certified rater who doesn't work for the installing contractor. That way the homeowner gets an unbiased check of the work. HERS raters are now called ECC raters under the 2025 Energy Code, but the job is the same. We schedule our work around the rater's visit so the permit can close out without extra trips.
How do I know if my ducts are leaking?
Common signs are rooms at the end of a run that stay warm in summer, dust that builds up fast, a hot or musty smell at the vents, bills that run higher than your neighbors', and an attic where old duct tape has dried out and fallen off. Flex duct that was stepped on or pulled loose from a boot is common in East County attics. A leakage test gives you a real number instead of a guess.
Can duct sealing fix a hot upstairs bedroom?
Sometimes. If the duct feeding that room is disconnected, crushed or leaking into the attic, sealing and repairing it can make a big difference. If the duct is simply too small, or the upstairs needs its own control, the fix may be resizing the run or adding zoning. We check airflow at the register so we can tell you which problem you have before you spend money on it.
Related services
All servicesBlue Star Heating & Air is just a call away!
If some rooms never get comfortable, or you're planning a system replacement, call (925) 584-2428. We'll look at your ducts and give you a written quote before any work starts.