Duct Sealing in San Mateo - Tested First, Written Price Second

Fast, Reliable Duct Sealing Across San Mateo

Duct sealing in San Mateo typically runs $1,200 – $2,800 for a whole-house job, with most homes falling in the $1,600 – $2,200 range depending on whether your system uses accessible flex duct or buried galvanized lines behind plaster. We’re Hollis Air Duct Cleaning, part of the Garrison Partners family, and our crews work San Mateo regularly from the Bay Area dispatch office, including our Dryer Vent Cleaning in San Mateo. We know the split personality of this city’s housing stock: the 1920s bungalows west of El Camino with gravity furnaces and original 4-inch galvanized ducts, versus the sealed high-rises near Hillsdale and Bay Meadows with shared rooftop RTUs. Each needs different equipment, different access strategy, and a technician who won’t treat a plaster-wall bungalow like a modern townhome. Call (361) 326-5060 for a free written estimate.

Call (361) 326-5060

Why Hollis Air Duct Cleaning Is San Mateo’s Preferred Duct Sealing Company

We’ve been in business since 2004, and our Duct Sealing team has worked enough San Mateo homes to know the difference between a Hillsdale tract house with flex duct in a crawlspace and a west-side bungalow with transite runs buried in plaster. That local knowledge matters because the wrong approach wastes your money and leaves the actual leaks untouched.

Our technicians are background-checked, uniformed, and held to The Garrison Code: arrive inside the quoted window, price in writing before touching anything, complete the job by the book, and leave the site clean. Every repair carries our 365-Day Done Right Promise in writing. If the seal fails within a year, we return 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 for someone in another state to route your request.

Duct Insulation in San Mateo

Duct Insulation in San Mateo is often the missing half of a sealing job, especially in the fog belt where uninsulated metal runs sweat against humid marine air and grow surface mold at the register boots. The job involves wrapping accessible trunk lines and plenums with formaldehyde-free fiberglass or foil-faced insulation, then sealing the vapor barrier so condensation can’t form between the duct wall and the insulation jacket. In San Mateo, we most often recommend insulation for homes with metal duct in vented crawlspaces or attics, where the temperature differential between the duct air and the surrounding space is greatest. Typical duct insulation here runs $800 – $1,500 when done with sealing, or $1,200 – $2,000 as a standalone job in larger homes with extensive trunk lines.

When Insulation Matters More Than Sealing Alone

Some San Mateo homes have tight ducts that still sweat. The 1960s ranchers in Parkside with uninsulated galvanized trunks in crawlspaces are a common example. Sealing stops air loss; insulation stops thermal loss and the condensation that follows. We assess both during our camera inspection and tell you which problem is actually driving your complaint.

Condensation in Fog-Belt Crawlspaces

San Mateo’s year-round dampness means crawlspace ducts never get a dry season. We’ve found standing water in crawlspace insulation jackets that looked intact from above. Our crews use moisture meters and borescopes to check the condition behind the wrap, not just the surface.

HVAC Duct Sealing in San Mateo

HVAC Duct Sealing in San Mateo covers the repair of leaks, gaps, and disconnected joints in forced-air distribution systems, using mastic paste, foil tape rated for ductwork, or mechanical fastening where access allows. The goal is to restore designed airflow to rooms that are too hot or too cold, reduce the dust and attic air being pulled into the system, and stop the pressure imbalances that make some San Mateo homes feel stuffy despite the windows staying closed against the fog. A typical HVAC duct sealing job in San Mateo runs $1,200 – $2,200 for single-family homes with accessible ductwork, or $2,000 – $2,800 for homes with buried galvanized lines requiring register-side repair.

Access Strategy for Buried Duct

West of El Camino, we regularly encounter original 4-inch galvanized or transite duct with no attic access and no crawlspace path. Our Duct Sealing in San Mateo crews use long-reach sealant applicators, register-mounted cameras, and negative-air containment to work from the inside out. It’s slower than wrapping a trunk line in an open joist bay, but it’s the only way to reach the actual leaks.

Shared-Building Systems Near Hillsdale and Bay Meadows

Newer condos and townhomes with rooftop RTUs use flex duct in tight chases. The failure mode here is usually crushed or disconnected flex at the boot, not seam gaps in rigid metal. We inspect with cameras before quoting, so you’re not paying for mastic work on a system that needs mechanical reconnection.

Trusted Brands We Service in San Mateo

We carry professional-grade equipment and materials from Rotobrush, Nikro, Abatement Technologies, and Guardsman, the same lines commercial crews use on larger Peninsula jobs. For San Mateo homeowners, that means we stock the right width of foil tape for narrow register boots, the correct mastic viscosity for overhead application in tight crawlspaces, and HEPA filtration rated for the fine particulate that older galvanized sheds. We don’t run to the hardware store mid-job. If your system uses Honeywell or Aprilaire filtration components, we can source and install compatible upgrades while we’re sealing. Parts are ordered through our Bay Area supply chain, so turnaround on non-stock items is typically a few days, not weeks.

Common Duct Sealing Problems We See in San Mateo Homes

• Mastic over mold, never removed. A previous crew smeared sealant over a wet, moldy duct stretch and called it done. The mold kept growing behind the seal, and the musty odor returned within a season. We HEPA-vacuum and source-remove first, then seal clean metal.
• Sealing the wrong ducts entirely. A west-side bungalow owner paid to have the crawlspace trunk wrapped, but the real leaks were in the buried 4-inch galvanized behind the bedroom plaster. The registers still whistled and the back bedroom stayed cold. We find the actual leaks with camera inspection before quoting.
• Fogging sold as sealing. A “sanitiser” fogging treatment leaves no mechanical seal, adds moisture to ducts already sweating in fog-belt air, and does nothing about pressure imbalance. We don’t offer fogging as a substitute for sealing. If your ducts are dirty, we clean under negative pressure first. If they’re leaking, we seal them.
• Ignoring transite and lead-safe requirements. Pre-1978 homes in San Mateo’s west-side neighborhoods may contain asbestos-cement duct or lead-painted surfaces. Disturbing these without proper survey and containment violates state rules and creates real health exposure. Our crews know the look of transite and stop for assessment when we see it.

Pricing for Duct Sealing in San Mateo, CA

We Also Serve Cities Near San Mateo

Our crews work throughout the mid-Peninsula, including San Mateo and neighboring Burlingame, Belmont, Millbrae, and San Carlos. The same fog-belt conditions, housing stock patterns, and access challenges apply across these communities, and we bring the same equipment and written guarantees to each job.

FAQs About Duct Sealing in San Mateo