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 Danville
Duct sealing in Danville typically runs $800 – $2,400 per HVAC system depending on accessibility and leak severity, and most homes here need each system assessed separately. We’re familiar with the large, multi-zone houses that define Danville’s housing stock, from the 1980s and 1990s builds in the San Ramon Valley to the estate properties in Blackhawk and Diablo. Our Duct Sealing team dispatches from our San Francisco Bay Area office, and we serve Danville homeowners with the same discipline we bring to every job: arrive inside the window, price it in writing before we touch anything, and leave the site clean. Call (361) 326-5060 for a free estimate.
Why Hollis Air Duct Cleaning Is Danville’s Preferred Duct Sealing Company
We’ve been in business since 2004 as part of the Garrison Partners family, and our reputation in Danville is built on showing up when we said we would. Homeowners here don’t have time for no-shows or crews that arrive in unmarked vans with prices that shift once they’re inside.
Our technicians are background-checked and uniformed, and we follow The Garrison Code on every job: written price before work starts, 365-Day Done Right Promise backed in writing, and a free second visit if the repair fails. Roy Castellanos leads our operation, and every Hollis location is independently owned and operated under The Garrison Standard.
Phones are answered by a live person 24 hours a day, 7 days a week. No voicemail loops, no callback queues, no waiting until Monday to schedule.
Duct Repair in Danville
Duct Repair in Danville addresses the cracked flex duct, failed plenum connections, and damaged supply boots that leak conditioned air into attics and crawlspaces. Most Danville homes built during the 1980s and 1990s suburban boom use original flex duct that has been flexing, sagging, and developing leaks for decades, especially in the hot, dry summers when attic temperatures spike past 130°F. A typical duct repair in Danville runs $400 – $1,200 per location depending on accessibility and whether the damage is localized or systemic.
Failed Connections at Supply Plenums
The connection between flex duct and the supply plenum is a common failure point in Danville’s older systems. Heat cycling and vibration loosen the original tape or clamp, creating a gap that dumps cooled air directly into the attic. We cut back to sound duct, secure with mechanical fasteners, and seal with mastic and mesh for a permanent fix.
Crushed or Collapsed Flex Duct Runs
Original flex duct in Danville attics often gets crushed by storage, compressed by insulation, or collapsed where it sags between supports. A crushed run acts like a dam, choking airflow to the rooms at the end of the line. We replace the damaged section with properly supported flex duct and verify airflow balance before we leave.
Air Duct Sealing in Danville
Air Duct Sealing in Danville closes the gaps, seams, and pinholes that leak conditioned air out of your duct system and pull unconditioned attic air in. In a typical Danville home with multiple HVAC zones, we often measure total leakage at 25 – 40% of system airflow, which means a quarter to nearly half of what you’re paying to cool is never reaching your living space. A complete air duct sealing job in Danville runs $800 – $2,400 per system depending on duct accessibility, system size, and whether we need to remove debris before sealing.
Mastic and Mesh Sealing Method
We seal accessible duct seams with duct sealing mastic reinforced with fiberglass mesh, not tape alone. Tape fails in attic heat; mastic remains flexible and airtight for the life of the system. We apply it to every joint, seam, and penetration we can reach, then verify with pressure testing where appropriate.
Pre-Sealing Source Removal
Sealing over ash, construction debris, or degraded flex liner traps contaminants in your system permanently. We use camera inspection and agitation tools to verify source removal before we seal, so the ductwork is clean and the sealant bonds to sound material. This step separates proper duct sealing from a quick tape job that fails in six months.
Trusted Brands We Service in Danville
We carry professional-grade equipment and materials from Rotobrush, Aprilaire, Abatement Technologies, and Guardsman, the same brands commercial crews specify for hospitals and schools. For Danville homeowners, that means we stock the right mastic, mesh, and flex duct locally, so we’re not ordering parts and making you wait. Our rotary brush systems and negative-air machines handle the large duct networks common in Danville’s multi-zone homes, and our filtration products from Honeywell and Aprilaire address the wildfire smoke and ash that has become a recurring concern in the San Ramon Valley.
Common Duct Sealing Problems We See in Danville Homes
- Multiple systems, one vague quote. A Danville home with three separate air handlers gets quoted as one sealing job, then the crew seals one system and leaves. Each system has its own supply and return ducts, its own leak profile, and its own line on a proper estimate.
- Accessible-only sealing. A technician seals the flex duct they can reach in the attic but ignores the long, hidden runs and air handler connections. The original leakage keeps pulling 130°F attic air into the system every time the blower cycles.
- Sealing over contamination. Wildfire ash and degraded flex liner get sealed into place instead of removed first. The ducts are technically sealed, but the homeowner is now circulating fine particulate every time the system runs.
- Tape-only repairs in attic heat. Standard duct tape fails in Danville’s hot attics within a year or two. We see homes where a previous “sealing” job is hanging in ribbons, and the leaks are worse than before.
Pricing for Duct Sealing in Danville, CA
A typical duct sealing job in Danville runs $800 – $2,400 per HVAC system. Single-system homes in the San Ramon Valley typically fall at the lower end; large Blackhawk and Diablo properties with three or more systems, extensive attic ductwork, or significant debris removal before sealing run higher. What moves the price: number of systems, accessibility of duct runs, whether camera inspection and source removal are needed before sealing, and the extent of damaged flex duct requiring repair rather than sealing alone.
We quote one flat price per system, agreed in writing before we start. No per-vent pricing, no add-ons at the door. Every estimate is free, and we explain exactly what each system needs and why. Call (361) 326-5060 for your exact quote.
We Also Serve Cities Near Danville
Our crews work throughout the San Ramon Valley and surrounding communities. We provide Duct Sealing in Danville and also serve San Ramon, Clayton, Alamo, and Dublin with the same written pricing, background-checked technicians, and 365-Day Done Right Promise.
Serving Danville, CA - Our Local Coverage Area
We’re based in the Danville 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 Danville
Each system is quoted and sealed separately because each has its own duct network, leak profile, and supply and return runs. A three-system home in Blackhawk or Diablo typically receives three separate line items on the written estimate, so you know exactly what each system costs before we start. Call (361) 326-5060 and we’ll walk through your home’s layout.
Homes built during Danville’s suburban boom used original flex duct that has now been expanding, contracting, and sagging for 30 – 40 years, creating leaks that newer duct materials and installation methods avoid. These older systems also tend to have less insulation and more attic exposure, so every leak pulls in hotter, dustier air. Call (361) 326-5060 for a free inspection of your system’s condition.
Duct sealing reduces the infiltration pathway, but only if combined with proper source removal first. We use camera inspection to locate ash deposits in returns and plenums, remove them with negative-air containment and agitation tools, then seal the system so it can’t pull in new contamination from the attic. Call (361) 326-5060 to discuss smoke-specific concerns for your home.
You should receive before-and-after photos from the camera inspection showing the interior condition of your ducts, a written description of what was sealed and where, and your copy of the written price agreement with the 365-Day Done Right Promise. We document every run we access because you deserve to know what was actually done in spaces you can’t enter yourself. Call (361) 326-5060 to schedule.
They are related but distinct: sealing closes gaps and seams in sound ductwork, while repair replaces crushed, disconnected, or degraded sections that sealing alone cannot fix. Many Danville homes need both, and we identify which applies during the free estimate so your written price covers exactly what your system needs. Call (361) 326-5060 for an exact assessment.
Written by Roy Castellanos, Owner at Hollis Air Duct Cleaning, serving Danville and the San Ramon Valley.