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.
Before
After
Before
After
Before
AfterFast, Reliable Duct Sealing Across Alamo
Duct sealing and Alamo Dryer Vent Cleaning typically run $800 – $2,400 for a whole-home job depending on system size and accessibility, and most projects are completed in a single day. We dispatch crews to Alamo from our San Francisco Bay Area coordination office, so we’re familiar with the winding roads off Danville Boulevard and the estate properties set back on half-acre lots where other services hesitate to quote without seeing the job first.
We’ve been working in Alamo long enough to know the pattern: a homeowner calls about a dusty house or a room that never reaches temperature, and the real problem isn’t the air handler or the filter. It’s the ductwork. Specifically, it’s the original galvanized trunk lines and flex runs installed in the 1960s through the 1990s that have worked loose, cracked, or disconnected entirely in attics nobody visits. Our Duct Sealing team finds the leaks, shows you the camera footage, and seals them with mastic and mesh so your system moves air through the rooms instead of into the crawlspace. Call (361) 326-5060 for a free estimate.
Why Hollis Air Duct Cleaning Is Alamo’s Preferred Duct Sealing Company
Alamo homeowners don’t call us because we’re the cheapest. They call us because we show up inside the window, price the job in writing before we touch anything, and leave the site clean. That’s The Garrison Standard, and it’s how every Hollis location operates, including ours serving Alamo.
Our technicians are background-checked and uniformed. You know who’s walking into your home before they arrive. Phones are answered by a live person 24 hours a day, 7 days a week, no voicemail loops. Every repair we perform carries the 365-Day Done Right Promise in writing: if the work fails within a year, we return and make it right at no charge, including a free second visit.
We know Alamo’s housing stock. The large custom homes on Alamo Ranch Road, the older estates near Livorna Estates, the properties backing up to the oak woodlands. We’ve crawled through enough attics here to recognize the smell of degraded flex duct insulation and the sight of a galvanized boot collar that’s been dumping conditioned air since the first Bush administration. That local knowledge means we diagnose faster and quote accurately the first time.
Duct Repair in Alamo
Duct Repair in Alamo usually means fixing what decades of heat, vibration, and settling have broken in homes built between the 1960s and 1990s. The job involves locating disconnected runs, replacing crushed flex duct, reattaching boots and collars, and sealing seams with mastic rated for HVAC use. A typical repair in Alamo runs $450 – $1,200 depending on how many runs need attention and whether we need to access them through finished spaces or unconditioned attics. Homeowners need duct repair when a room suddenly won’t heat or cool, when energy bills spike without explanation, or when a camera inspection reveals a disconnected trunk line dumping air into the attic.
Disconnected Trunk Lines
Original galvanized trunk lines in Alamo’s older estates often separate at boot collars where the metal meets the flex run. The connection loosens from thermal expansion, vibration, and the weight of decades of dust accumulation. We find these with a camera scope, reseat the collar, and seal the joint with mastic and fiberglass mesh so it stays put.
Crushed Flex Runs
Flex duct behind knee walls or buried in attic insulation gets crushed by storage boxes, compressed by new insulation blown over old, or simply collapses from age. A crushed run doesn’t move air. We replace the damaged section with new flex duct sized to the original specification and seal both ends properly.
Air Duct Sealing in Alamo
Air Duct Sealing in Alamo addresses the smaller leaks that don’t disconnect entirely but bleed conditioned air into attics, crawlspaces, and wall cavities all day long. The process starts with a pressure test to quantify leakage, followed by manual sealing of accessible joints with mastic and mesh, and sometimes aerosolized sealant for leaks inside finished walls. A whole-home sealing job in Alamo typically costs $800 – $2,400, with most falling in the $1,200 – $1,800 range for a 3 – 4 zone system. You need sealing when rooms have uneven temperatures, when dust seems to reappear immediately after cleaning, or when your energy bills are higher than neighbors with similar homes.
Pressure Testing First
We pressurize your duct system and measure total leakage against the conditioned square footage. Alamo’s older homes often test at 25 – 40% leakage, meaning a quarter to nearly half the air your system produces never reaches a register. The test gives us a baseline and proves the improvement after sealing.
Mastic, Not Tape
Foil tape fails in attics. The adhesive cooks off, the tape curls, and the leak returns. We use water-based duct mastic rated for temperature extremes, reinforced with fiberglass mesh on joints that move or flex. In Alamo’s 140-degree summer attics, that matters.
Trusted Brands We Service in Alamo
Our equipment roster includes Nikro negative-air machines for source removal, Honeywell and Aprilaire filtration products, and Abatement Technologies HEPA containment systems. We don’t show up with hardware-store gear. For Alamo homeowners, that means we can source replacement components and filtration upgrades without waiting on national distribution. If your system needs a media cabinet upgrade after sealing, we stock Aprilaire and Honeywell frames and filters sized to common Alamo installations. Turnaround on most sealing jobs is same-day completion; if we find a component that needs ordering, our Bay Area supply relationships usually have it within 24 hours.
Common Duct Sealing Problems We See in Alamo Homes
- Heat-cooked flex duct in second-floor attic runs. Alamo’s summer attic temperatures degrade the outer vapor barrier and inner liner of flex duct serving bedrooms and bonus rooms. The damage happens years before any register feels weak, so sealing is deferred until the run is already crushed or disconnected.
- Galvanized trunk seam separation in 1960s – 1990s estates. Original metal trunk lines lose their factory tape and boot collar seals over decades. The leaks dump conditioned air into unconditioned spaces where the loss never produces an obvious comfort complaint, just a system that runs constantly.
- Return-side leakage pulling in wildfire smoke and oak pollen. Alamo’s location in the Diablo Valley puts it downwind of grass and oak pollen sources, and increasingly in the path of wildfire smoke. Leaky return ducts draw these contaminants in and recirculate them through the air handler, turning a sealing problem into an indoor air quality issue for sensitive residents.
- Disconnected boots at attic knee walls. The transition from hard duct to flex at the boot collar is a common failure point in Alamo’s older homes, especially where knee walls create vibration points or where storage in bonus rooms has compressed the flex run against the boot.
Pricing for Duct Sealing in Alamo, CA
Whole-home duct sealing in Alamo typically runs $800 – $2,400. Most 3 – 4 zone homes in the Stone Valley or Round Hill neighborhoods fall in the $1,200 – $1,800 range. Single-run repairs or partial sealing of a problematic zone start around $450. What moves the price: how many attic or crawlspace access points we need to open, whether we’re working around existing insulation, and whether the system needs a pressure test and pre/post verification. We do not quote per-vent pricing. We quote one flat price per system, agreed in writing before work starts. That price does not move at the door. Estimates are free, and we show you the camera footage so you see what we see. Call (361) 326-5060 to schedule.
We Also Serve Cities Near Alamo
Our crews work throughout the Diablo Valley, including Duct Sealing in Alamo and surrounding communities. We regularly service Walnut Creek, Moraga, Lafayette, and Danville with the same written pricing, background-checked technicians, and 365-Day Done Right Promise.
Serving Alamo, CA - Our Local Coverage Area
We’re based in the Alamo 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 Alamo
It very likely is. In Alamo’s 1970s homes, the flex duct run to the bonus room was typically installed through a hot attic with minimal insulation, and the boot collar connection at the trunk line is a common failure point. We see this exact symptom on Alamo Ranch Road and in the Livorna Estates area regularly. The fix is usually a camera inspection to locate the disconnection or crush point, followed by repair and sealing. Call (361) 326-5060 and we’ll scope it.
We pressurize the system and use a calibrated manometer to measure total leakage, then run a borescope camera through the trunk lines and accessible flex runs. In Alamo’s older homes, we typically find the worst leaks at galvanized boot collars and at points where flex duct passes through hot attic spaces near the roof deck. The camera footage shows you exactly what we found before we quote any sealing work.
Yes, significantly. Leaky return-side ducts in Alamo homes pull attic air and outside contaminants directly into the system. During Diablo wind events and wildfire season, that means smoke and ash. During spring, it means valley oak pollen. Sealing the return ductwork eliminates those infiltration paths. We verify the improvement with a post-seal pressure test.
Most original galvanized trunk lines in Alamo’s 1960s – 1990s homes can be sealed successfully if the metal itself is intact. We reseam the longitudinal joints, reattach boot collars with mastic and mesh, and replace any damaged flex branches. Replacement of the entire trunk is only necessary if the metal has corroded through or been damaged by rodents. We’ll show you the camera footage and tell you which category you’re in before any work starts.
The most common first sign is a room that never reaches the thermostat setting, especially a second-floor bedroom or bonus room in summer. The second is dust that returns quickly after cleaning, because leaky supply ducts pressurize wall cavities and leaky returns pull that dust back in. If either sounds familiar, call (361) 326-5060 for a free inspection.
Written by Roy Castellanos, Owner at Hollis Air Duct Cleaning, serving Alamo and the San Francisco Bay Area since 2004.