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 Daly City
Duct sealing in Daly City typically runs $800 – $2,400 for a whole-house system, depending on whether we’re sealing accessible joints or rebuilding corroded galvanized runs in crawlspaces. Most jobs take one day, and we’ll give you a written price before any work starts. Call (361) 326-5060 for a free estimate.
We’ve worked in Daly City long enough to know the difference between a quick tape job and a real seal that holds up. Our crews serve Daly City from our San Francisco Bay Area dispatch office, and we understand what the marine layer does to post-WWII ductwork. Homes off John Daly Boulevard, in Westlake, and up toward Top of the Hill all share the same problem: original galvanized steel that corrodes in persistent dampness, joints that separate, and crawlspaces where fog-laden air condenses inside the ducts. We don’t just seal what we can see. We inspect the full system, repair what’s broken, and seal it so the fix lasts.
Why Hollis Air Duct Cleaning Is Daly City’s Preferred Duct Sealing Company
Hollis Air Duct Cleaning has been part of the Garrison Partners family since 2004. That track record matters in Daly City, where homeowners have seen plenty of fly-by-night outfits tape a few joints and disappear. We’re still here because we do the work by the book.
Every Hollis technician is background-checked and uniformed. You know who’s walking into your home before they arrive. The price is written down before any work starts, and it does not move at the door. Our Duct Sealing team operates under The Garrison Standard: arrive inside the quoted window, price in writing, complete the job by the book, leave the site clean. And every repair is backed by our 365-Day Done Right Promise. If the work fails within a year, we come back and make it right at no charge, including a free second visit.
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.
Duct Repair in Daly City
Duct Repair in Daly City usually means fixing the damage we find inside original 1940s – 1960s galvanized steel systems: crushed runs, disconnected boots, and corrosion holes that leak heated air into crawlspaces and attics. We see this constantly in the post-WWII tract homes that make up so much of Daly City’s housing stock. A typical repair runs $400 – $1,200, depending on accessibility and how much material needs replacing.
Crushed and Disconnected Runs
Flexible duct gets crushed by storage, pests, or decades of settling. Rigid galvanized separates at the seams. We replace crushed flex with new insulated duct, reconnect separated joints with mechanical fasteners, and seal with mastic and mesh. Foil tape alone won’t survive Daly City’s coastal corrosion.
Corroded Galvanized Sections
Original steel ductwork in Daly City homes rusts from the inside out where condensation pools. We cut out corroded sections and splice in new galvanized or switch to insulated flex where appropriate, sealed to prevent the moisture intrusion that caused the original failure.
Air Duct Sealing in Daly City
Air Duct Sealing in Daly City costs $800 – $2,400 for a complete system, with most homeowners paying between $1,100 and $1,800. The price depends on duct material, accessibility, and whether we need to pair sealing with antimicrobial treatment and moisture control. Sealing alone isn’t enough here.
Mastic, Mesh, and Mechanical Fasteners
We seal joints with duct mastic reinforced with fiberglass mesh, plus mechanical fasteners on corroded steel. Foil tape fails within a season or two in Daly City’s damp crawlspaces. The marine layer keeps everything moist, so adhesive-backed solutions don’t hold.
Moisture Control and Antimicrobial Treatment
In Daly City, duct sealing must be built for a wet environment, not just an airtight one: post-WWII galvanized steel runs corrode and the marine layer keeps them damp, so a seal alone can trap moisture and feed mildew, which is why we pair sealing with moisture control and antimicrobial treatment. We apply EPA-registered antimicrobial products from Guardsman and Abatement Technologies after source removal, then seal so the system stays clean and dry.
Trusted Brands We Service in Daly City
We carry equipment and parts from Aprilaire, Abatement Technologies, and Guardsman, so Daly City homeowners aren’t waiting on special orders. Our rotary brush systems from Rotobrush and negative-air machines from Nikro handle the source removal that must precede any seal. When we find a failed Aprilaire media filter or need Guardsman antimicrobial treatment for a mold-affected system, we’ve got it on the truck or can get it fast. That matters in Daly City, where the damp climate means delays let mold keep growing.
Common Duct Sealing Problems We See in Daly City Homes
- Contractors seal the easy joints and skip the crawlspace. We find this constantly: shiny tape at the air handler and registers, but the original galvanized trunk in the crawlspace still leaks fog-damp air. Daly City’s condensation-prone ductwork keeps sweating and re-soiling the system until someone seals the full run.
- Sealing over mold without treatment. Sealing over dirty, damp galvanized duct interiors without source removal or antimicrobial treatment traps black mold spores inside the sealed cavity, which is a common Westlake mistake we are often called to correct. The homeowner smells musty air for months before realizing the seal made it worse.
- Foil tape on corroded steel. Using standard foil tape instead of mastic, mesh, and mechanical fasteners on corroded 1940s – 1960s steel fails within a couple of seasons because coastal corrosion eats the adhesive and the joint opens back up. We’ve peeled failed tape off ducts in Daly City that were “sealed” two summers ago.
- Disconnected returns dumping damp air. In split-level homes near Westlake’s Gateway Boulevard, we regularly find return boots disconnected in unheated crawlspaces, pulling in marine-layer air for years. The system runs longer, costs more, and the homeowner can’t figure out why the back bedrooms stay cold and damp.
Pricing for Duct Sealing in Daly City, CA
A typical duct sealing job in Daly City runs $800 – $2,400. Partial sealing of accessible joints starts around $800. Full-system sealing with crawlspace access, antimicrobial treatment, and moisture control usually falls between $1,100 and $1,800. If we’re rebuilding corroded galvanized sections or replacing crushed flex runs, costs can reach $2,400.
What moves the price: accessibility (crawlspace height, attic entry), extent of corrosion damage, whether mold remediation is needed before sealing, and how many disconnected or crushed runs we find. We inspect with a camera before quoting, so you see what we see. The price is written down before any work starts. One flat price per system. No per-vent add-ons, no surprises at the door.
We also provide before-and-after photos of your own ducts, so you know the work was done. Call (361) 326-5060 for a free estimate.
We Also Serve Cities Near Daly City
Our crews work throughout the northern Peninsula. We also provide duct sealing and repair in Daly City‘s neighboring communities: Brisbane, South San Francisco, San Bruno, and Pacifica. The same marine-layer conditions affect homes in all these cities, and we bring the same inspection, repair, and sealing process to each job.
Serving Daly City, CA - Our Local Coverage Area
We’re based in the Daly City 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 Daly City
Daly City’s extreme marine layer and persistent dampness keep duct interiors moist year-round, while sunnier inland cities dry out naturally. In neighborhoods like Westlake, technicians often find black mold inside return ducts due to decades of fog infiltration, a condition rarely seen even a few miles inland. The combination of original galvanized steel, unheated crawlspaces, and constant humidity creates perfect conditions for mold. Call (361) 326-5060 if you smell musty air from your vents.
Yes, if the cold and damp come from leaks pulling in crawlspace or attic air, which is common in Daly City’s split-level and post-WWII tract homes. We were called to a 1950s split-level off Westlake’s Gateway Boulevard after a homeowner with asthma noticed musty odor coming from the supply and return ducts. Camera inspection showed the original galvanized main trunk running through an unheated crawlspace with two crushed runs and a disconnected return boot that had been dumping fog-damp air for years. After negative pressure source removal and antimicrobial treatment, we sealed the joints with mastic and mesh, sealed the disconnected return boot, and the blower motor’s static pressure dropped enough that the system finally moved air to the back bedrooms without that damp, moldy smell. Call (361) 326-5060 for an inspection.
It can. Daly City’s damp coastal air corrodes original galvanized steel faster than inland climates, so we often find sections that need repair or replacement before sealing. A straightforward seal job runs $800 – $1,400, but if we’re rebuilding corroded trunk lines or replacing crushed runs, costs rise toward $1,800 – $2,400. We camera-inspect first and give you a written price before any work starts. Call (361) 326-5060 for a free estimate.
Sealing over active mold makes the problem worse by trapping spores in a dark, moist cavity. We start with negative-air source removal using Nikro equipment, apply antimicrobial treatment from Guardsman or Abatement Technologies, then seal with mastic and mesh once the system is clean and dry. This three-step process adds $300 – $600 to a standard sealing job but prevents the sealed system from becoming a mold incubator. Call (361) 326-5060 to schedule an inspection.
We determine this with a camera inspection. If the galvanized steel has pinhole corrosion or separated seams but retains structural integrity, sealing and targeted repair usually suffice. If the trunk line is riddled with corrosion holes, collapsed sections, or heavy mold penetration, replacement becomes the better long-term value. We’ll show you the camera footage and explain both options with written prices for each. Call (361) 326-5060 to book an inspection.
Written by Roy Castellanos, Owner at Hollis Air Duct Cleaning, serving Daly City and the Bay Area since 2004.