Fast, Reliable Duct Repair & Sealing Across Sunnyvale
Duct repair and sealing in Sunnyvale typically costs $280-$750 for standard jobs, with full liner replacement in older homes running $1,200-$2,800. Most repairs are completed in a single visit, and we answer calls live 24 hours a day at (844) 685-6342. If your home dates to the Lockheed or early semiconductor era, there’s a fair chance your ductwork has never been opened since the day it was installed.
We’ve been driving to Sunnyvale since 1984, long before the 101 was widened through the Moffett corridor. Our technicians know the difference between a 1958 ranch off Mathilda and a 1972 Eichler-style tract near Fair Oaks, and they know what kind of ductwork each one hides. We don’t guess. We run a camera through the system first, show you what we find, and give you one honest price before we pick up a single tool. That’s how we’ve operated for over 42 years, and it’s not changing now.
Why Bellows Air Duct & Vent Co. Is Sunnyvale’s Preferred Duct Repair & Sealing Company
Sunnyvale homeowners call us back because we don’t bait-and-switch. Our Duct Repair & Sealing team has handled everything from minor seam re-taping in a 94085 condo to full liner replacement in 94086 ranches built for Lockheed engineers. We show up in marked vans, in uniform, and we don’t send anyone to your home who hasn’t passed a background check.
Our 90-Day Done Right Promise applies to every job in Sunnyvale. If the seal doesn’t hold, if the liner we installed sheds fiber, or if the mastic cracks, we return at no charge. No paperwork to file, no argument. Ray Castillo put that in writing when he founded this company, and it still stands.
Calls are answered by a live person, not an app or a voicemail tree. That matters when you’re running your HVAC on recirculate during a smoke event and you can smell something burning in the ducts. We’ll be there when we say.
We also offer a free second opinion on any written estimate you’ve already received, $50 off any repair over $250, and a permanent 5% discount for seniors and veterans. The price we quote is the price on the invoice. No surprises on the bill.
Our Duct Repair & Sealing Services in Sunnyvale
Duct Sealing
Most Sunnyvale homes lose 20-30% of conditioned air through leaks before it reaches the room. In the 94086 and 94087 ZIPs, we find cracked sheet-metal joints in crawl spaces that have been thermally cycling since the Kennedy administration. We pressurize the system, locate every leak with a smoke pencil, and seal with mastic or metal-backed tape rated for ductwork. Not duct tape. Real duct tape. The difference shows up on your PG&E bill and in rooms that finally heat evenly.
Flex Duct Repair
Original flex duct runs in Sunnyvale’s older homes are collapsing under their own weight after sixty years. The spiral wire frame rusts, the plastic liner cracks, and the fiberglass insulation compacts into a dense mat that restricts airflow. Your blower works harder, your energy bill climbs, and the taped seams blow out under the extra pressure. We replace collapsed runs with new insulated flex duct, properly supported and sealed, so air moves the way it was meant to.
Metal Duct Repair
The sheet-metal trunk lines in Lockheed-era Sunnyvale homes were built to last, but the internal fiberglass liner wasn’t. We regularly open 1960s metal ducts and find the liner has delaminated into loose batting that sheds glass fibers every time the blower kicks on. Our crew recently worked a 1963 ranch home on Springer Road in the 94086 ZIP. The owner’s HVAC had been pulling in smoke particles from the 2018 Camp Fire, and we found the original sheet-metal duct liner had delaminated into loose batting. We had to cut out six 8-foot sections and apply new mastic-sealed internal insulation to stop fiber re-entry. Metal duct repair in Sunnyvale often means metal duct rehabilitation, and we’re equipped for both.
Duct Insulation & Mastic Sealant
Sunnyvale’s dry summers mean humidity-driven mold is rare, but uninsulated or poorly sealed ductwork in crawl spaces loses conditioned air to the soil year-round. We apply professional-grade mastic sealant, a thick, brush-on compound that fills gaps and remains flexible for decades, then wrap with new insulation where needed. For homes with intact metal ducts but failed liners, we install new internal insulation sealed with mastic at every joint. The result is a system that handles wildfire smoke season without recirculating old fiberglass and accumulated silicon-valley construction dust back into your living room.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Sunnyvale
We carry parts and materials from Nikro, Honeywell, and Aprilaire on every truck serving Sunnyvale. That means when we find a failed damper actuator in a 94087 crawl space or a broken inline filter housing in a 94085 townhome, we don’t have to order parts and come back next week. Most jobs finish in one visit. The brands we use are the same ones serious HVAC contractors specify for new construction, not the discount hardware-store stock that cracks in two seasons. When you’re already dealing with sixty-year-old ductwork, the last thing you need is a repair that fails before the next wildfire smoke event.
Common Duct Repair & Sealing Problems We See in Sunnyvale Homes
- Delaminated internal fiberglass liner shedding glass fibers. In Sunnyvale’s Lockheed-era tract homes, original internally-lined fiberglass ductwork from the 1950s-1970s frequently sheds glass fibers and traps wildfire PM2.5, turning a routine sealing job into a full interior liner replacement. Technicians working older Sunnyvale crawl-space systems frequently pull duct sections whose original factory-applied internal fiberglass liner has completely delaminated after 50-plus years.
- Cracked sheet-metal joints from decades of thermal cycling. The crawl spaces and attic chases in 94086 and 94087 ranches see temperature swings from 45°F winter nights to 140°F summer attic peaks. Metal expands, contracts, and eventually splits at the seams. We measure the leakage with a duct blaster before we start and verify the seal after we finish.
- Collapsed flex duct runs restricting airflow and overloading blowers. Original flex duct in Sunnyvale’s 1960s and 1970s tracts has compressed into oval or flattened shapes that choke airflow. The blower compensates by running longer and harder, which blows out taped seams and drives up your electric bill.
- Original duct systems engineered for 1960s filtration standards. Sunnyvale’s increasing wildfire smoke seasons push concentrations of fine particulate matter deep into duct systems that were never designed for continuous recirculation with modern MERV filters. Sealing leaks helps, but if the liner is degraded, the system needs more than sealing.
Pricing for Duct Repair & Sealing in Sunnyvale, CA
Here’s what honest pricing looks like for Sunnyvale’s market. These are the ranges we quote before we start, and they’re consistent with what we’ve charged across Santa Clara County for years.
- Duct sealing (mastic, minor leak repair): $280-$450
- Flex duct section replacement: $180-$340 per run
- Metal duct joint repair and resealing: $320-$580
- Internal liner replacement (per 8-foot section): $240-$380
- Full duct liner replacement, typical 1,200 sq ft ranch: $1,200-$2,800
- Duct insulation wrap (crawl space or attic): $450-$890
What moves the needle: accessibility (crawl space height, attic hatch location), extent of liner damage, and whether we can reach the ductwork without cutting access panels. We inspect with a camera first, so you see exactly what we see before you decide. Estimates are free. Call (844) 685-6342 to schedule.
Standing offers: $50 off any repair over $250, free second opinion on any written estimate, $89 seasonal tune-up, and permanent 5% senior and veteran discount.
We Also Serve Cities Near Sunnyvale
Our service area covers the full South Bay corridor. We regularly handle Duct Repair & Sealing in Sunnyvale and neighboring Mountain View, Santa Clara, Cupertino, and Los Altos. The same camera inspection, same upfront pricing, same 90-Day Done Right Promise applies whether you’re off El Camino Real or up in the Los Altos Hills.
Serving Sunnyvale, CA - Our Local Coverage Area
We’re based in the Sunnyvale 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 - Duct Repair & Sealing in Sunnyvale
If your 1964 ranch still has original internally-lined fiberglass ductwork, sealing leaks alone won’t stop glass fiber shedding. We run a camera first. If the liner is intact, mastic sealing and joint repair may be enough. If it’s delaminated, partial or full liner replacement is the only fix that stops fiber re-entry. Call (844) 685-6342 and we’ll show you what the camera sees, no charge for the inspection.
Duct sealing reduces smoke infiltration from leaks, but it won’t remove PM2.5 already embedded in degraded fiberglass liner. In 94086 homes with original Lockheed-era ductwork, we frequently find wildfire particles trapped in crumbling liner material that recirculates every time the blower runs. Sealing plus liner replacement is often necessary for full relief. We can test with a camera inspection and give you a clear answer.
The rattle usually comes from loose sheet-metal joints that have separated after sixty years of thermal cycling, or from collapsed flex duct sections vibrating against framing. Wildfire season makes it worse because you’re running the blower continuously on recirculate, amplifying every loose connection. We isolate the source with a camera and pressure test, then secure and seal the affected sections. Most rattles we fix in Sunnyvale trace back to two or three specific joints that have been loose since the Reagan administration.
You don’t need to cut drywall. We access ductwork through existing registers and boot connections, then run a borescope camera through the system. If the liner is delaminated, you’ll see loose fiberglass batting on the monitor, often gray with decades of dust. We document everything and email you the footage. In Sunnyvale’s 94086 and 94087 ZIPs, we find delaminated liner in roughly half the pre-1975 homes we inspect. The camera doesn’t lie, and the inspection is free with any service call.
Mastic sealant is excellent for sealing joints and small gaps in intact metal ductwork, but it cannot replace failed internal insulation. If your 1960s sheet-metal ducts still have sound liner, mastic sealing at joints and seams is the right repair and will last decades. If the liner has delaminated, mastic alone leaves you with bare metal that sweats in winter and sheds accumulated particulates year-round. We determine which situation you have before we recommend anything. Call (844) 685-6342 for a camera inspection and an exact quote, estimates are free.
Ready to stop losing conditioned air and breathing sixty-year-old fiberglass? Call Bellows Air Duct & Vent Co. at (844) 685-6342. We’ll answer live, schedule at your convenience, and show up with a camera, a clear price, and the tools to finish the job in one visit. We’ve served this area for over 42 years. We stand behind it, no paperwork, no arguing.
Written by Ray Castillo, Owner at Bellows Air Duct & Vent Co., serving Sunnyvale since 1984.