Whole-system duct and dryer vent check with before-and-after photos - you see exactly what came out of your vents
That "$99 whole-house special" is a bait ad - the real number appears once they are in your hallway, or the "clean" is a shop-vac at the register. We photograph the inside of your ducts before and after instead.
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AfterFast, Reliable Duct Sealing Across Hillsborough
We dispatch to Hillsborough from our San Francisco Bay Area office, and crews are usually on-site within a day or two of your call. If you live in Hillsborough and you’re noticing uneven temperatures between rooms, a musty smell when the heat kicks on, or utility bills that keep climbing, your ductwork is likely leaking conditioned air into your attic or crawlspace. Call us at (361) 326-5060 for a free estimate. We’ll show up in the window we promised, price the work in writing before we touch anything, and back it with our 365-Day Done Right Promise.
Why Hollis Air Duct Cleaning Is Hillsborough’s Preferred Duct Sealing Company
Hollis Air Duct Cleaning has been part of the Garrison Partners family since 2004, and our Bay Area crews know Hillsborough’s housing stock intimately. We’ve sealed ducts in estates off El Camino Real, worked on mid-century homes near Skyline Boulevard, and tracked down leaks in retrofit systems above the Canyon Road corridor. Our technicians are background-checked, uniformed, and expected to operate by The Garrison Code: arrive inside the window, price in writing, complete the job by the book, and leave the site clean.
Phones are answered by a live person 24 hours a day, 7 days a week. No voicemail loops. No callback queues. When you schedule Duct Sealing with Hollis, you get a written price before any work starts and a 365-Day Done Right Promise that covers every repair. If the work fails within a year, we return and make it right at no charge, including a free second visit.
HVAC Duct Sealing in Hillsborough
HVAC Duct Sealing in Hillsborough is primarily about stopping conditioned air from escaping through gaps, disconnected collars, and deteriorated seams in ductwork that runs through attics and crawlspaces beneath wooded lots. Because Hillsborough estates sit under mature oak, redwood, and eucalyptus canopy on wooded lots, the first big fall storm pushes damp leaf litter and roof debris into outdoor intakes and return ducts, producing a musty smell that shows up here weeks before it does in sunnier, less-wooded Peninsula towns. Sealing the duct system at every joint, seam, and penetration prevents this moisture-laden air from being pulled into your HVAC and distributed through your home.
A typical HVAC duct sealing job in Hillsborough runs $1,200 – $2,800 for a single-zone system, with multi-zone estates ranging $2,800 – $5,500 depending on total linear footage and accessibility. We use professional-grade mastic and foil-backed tape, not the hardware-store duct tape that fails in six months.
Sealing Multi-Zone Estates
Many Hillsborough homes have multiple HVAC zones added over decades. Our crews seal the trunk lines, branch ducts, and air handler cabinets for each zone, then pressure-test the entire system to verify no bypass leaks between zones.
Mastic vs. Tape Application
We apply duct sealing mastic, a thick, fiber-reinforced compound that remains flexible and airtight for years, at every joint and seam. Foil-backed tape reinforces the mastic at high-stress points. This combination outlasts any adhesive-only method.
Duct Repair in Hillsborough
Duct Repair in Hillsborough often involves replacing crushed flex duct, reconnecting separated collars, and patching holes where original galvanized ducting has corroded at the seams. Hillsborough’s housing stock is dominated by large, architecturally varied single-family estates built from the 1920s through the 2000s, with a mix of original mid-century systems, retrofitted zoning, and newer high-efficiency units. This means ductwork often includes a combination of original galvanized or flex ducts in older wings and modern rigid ducting in additions, requiring careful inspection for disconnected or crushed runs.
Typical duct repair in Hillsborough costs $400 – $1,200 for isolated fixes, with extensive replacement of multiple runs reaching $1,800 – $3,500. We always inspect the full system, because fixing one visible leak while leaving three hidden ones wastes your money.
Crushed Flex Duct Replacement
Flex duct in older wings sags and tears where it passes over hot attic joists, creating leaks that pull in damp leaf litter and pollen from the surrounding canopy. We replace damaged runs with properly supported rigid ducting where access allows, or with new flex duct on gradual slopes that won’t pool condensation.
Disconnected Collar Reconnection
Supply and return collars separate over years of thermal expansion and vibration. We reseat each collar, secure it with mechanical fasteners, then seal with mastic to prevent the joint from leaking again.
Trusted Brands We Service in Hillsborough
Our crews carry parts and sealing materials compatible with systems from Aprilaire, Abatement Technologies, and Guardsman, plus we stock mastic, foil tape, and rigid ducting for fast turnaround on Hillsborough jobs. We also work with Rotobrush rotary brush systems and Nikro negative-air machines when duct cleaning precedes sealing. Most Hillsborough estates use Honeywell or Aprilaire filtration components, and we verify filter fit and seal integrity as part of every duct sealing job. If your system uses less common components, we source them quickly rather than making you wait.
Common Duct Sealing Problems We See in Hillsborough Homes
- Fall storm debris infiltration. After the first big October storm, outdoor intake screens clog with eucalyptus leaves and redwood needles, allowing moisture-laden air to enter the return and accelerate microbial growth inside the duct lining. Sealing the intake penetration and upgrading the screen prevents recurrence.
- Retrofit zoning damper leaks. Retrofitted zoning dampers installed in original galvanized trunks often leak at the seams, so sealing the ducts without sealing the damper frames leaves a hidden bypass. We seal both.
- Original galvanized duct corrosion. Pre-1970s galvanized ducting in Hillsborough’s older estates corrodes at seams and hangers, creating pinhole leaks that compound over decades. We patch where possible and replace where the metal is too thin to hold a seal.
- Attic flex duct over hot joists. Flex duct routed directly over attic joists without support sags, tears, and leaks conditioned air into the attic. We add support straps and replace damaged sections.
Pricing for Duct Sealing in Hillsborough, CA
Duct sealing in Hillsborough typically runs $1,200 – $2,800 for single-zone systems and $2,800 – $5,500 for multi-zone estates, with duct repair adding $400 – $1,200 for isolated fixes or $1,800 – $3,500 for extensive replacement. What moves the price: total linear footage of ductwork, number of zones, attic vs. crawlspace access, and whether we find damaged ducting that needs replacement before sealing can be effective.
We give you one flat price per system, agreed in writing before any work starts. No per-vent pricing. No add-ons at the door. Call (361) 326-5060 for an exact quote. Estimates are free.
We Also Serve Cities Near Hillsborough
Hollis Air Duct Cleaning provides Duct Sealing in Hillsborough and surrounding communities, including Los Angeles, San Diego, San Jose, and San Francisco. Each location is independently owned and operated under The Garrison Standard.
Serving Hillsborough, CA - Our Local Coverage Area
We’re based in the Hillsborough area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About Duct Sealing in Hillsborough
The smell comes from damp leaf litter, pollen, and roof debris pulled into outdoor intakes and return ducts when storms hit Hillsborough’s dense oak, redwood, and eucalyptus canopy. Sealing the duct system at all penetrations and upgrading intake screens stops this infiltration at the source. Call (361) 326-5060 for an exact quote. Estimates are free.
Fogging does not fix the problem. It masks odor temporarily while leaving the leak open for new moisture and debris to enter. Duct sealing closes the actual gaps and disconnected joints that allow infiltration, which is the only lasting solution for Hillsborough’s wooded-lot conditions. Call (361) 326-5060 for an exact quote. Estimates are free.
Sealed ducts prevent negative pressure in your return system from pulling outdoor air through gaps in attic and crawlspace runs, which is how wildfire ash and smoke enter during Peninsula fire seasons. A sealed system with proper filtration removes this pathway entirely. Call (361) 326-5060 for an exact quote. Estimates are free.
Yes. We inspect each section, seal compatible joints with mastic and mechanical fasteners, and replace corroded galvanized where it won’t hold a seal. We were called to a 1970s estate off Manzanita Drive after the first October storm, where the homeowners reported a musty smell and uneven airflow in the primary bedroom wing; our camera inspection found a crushed flex duct in the attic run and a disconnected collar at a supply register above the rear addition, so we re-sealed the collar with mastic, replaced the crushed run with rigid ducting, and sealed the air handler cabinet and remaining supply and return ducts, restoring balanced airflow and eliminating the odor source. Call (361) 326-5060 for an exact quote. Estimates are free.
Most Hillsborough estates benefit from inspection every 3 – 5 years, with sealing or repair as needed. Homes with original galvanized ducting or multiple retrofit zones may need more frequent attention. After any major storm or wildfire event, a camera inspection is worth the cost. Call (361) 326-5060 for an exact quote. Estimates are free.
Written by Roy Castellanos, Owner at Hollis Air Duct Cleaning, serving Hillsborough since 2004.