Fast, Reliable Duct Repair & Sealing Across Mission District
Duct repair and sealing in Mission District typically costs $280-$650 for most homes, with same-day service available when you call before noon. We’re Bellows Air Duct & Vent Co., and we’ve been driving our vans down Valencia Street and threading through Mission alleys since 1984. Our Duct Repair & Sealing team knows the parking situation near 24th Street BART, the narrow crawl spaces beneath Victorian flats on Shotwell, and how to carry equipment through alley-load entries that weren’t built for modern HVAC gear. If your ducts are leaking, rattling, or blowing dust through original fir-floor cavities, call us at (844) 685-6342. We’ll answer live, 24 hours a day, and most repairs are finished in a single visit.
Why Bellows Air Duct & Vent Co. Is Mission District’s Preferred Duct Repair & Sealing Company
We’ve worked in Mission District long enough to know which buildings on Capp Street have the original 1910 crawl-space hatches, and which blocks near Dolores Park require us to stage equipment on the sidewalk with proper permits. That familiarity saves time. Our technicians don’t waste half an hour figuring out how to access your system.
Our reputation here is built on showing up when we say and leaving the job finished. The 90-Day Done Right Promise is stamped on every invoice, and it means exactly what it says: if something isn’t right, we return at no charge with no paperwork required. Ray Castillo, our owner, has insisted on this since 1984.
Calls are answered by a live person, not an app or a menu. That’s especially important when you’re standing in a Mission flat at 10 PM with a duct that’s come completely loose and is banging against floor joists every time the furnace cycles.
Every technician is background-checked and uniformed. Every job gets a camera inspection before and after, so you see what we see. No claims without proof.
Our Duct Repair & Sealing Services in Mission District
Duct Sealing with Mastic Sealant
Mastic sealant is the only proper way to seal joints in Mission District’s retrofitted duct systems. Tape dries out. Spray foam cracks. We apply Guardsman mastic by hand to every joint, sleeve, and penetration, then verify the seal with a pressure test. In Victorians where ducts were forced through wall chases never designed for airflow, mastic is often the difference between a system that loses 30% of its air and one that performs as intended. Our mastic sealing jobs in Mission District run $280-$420 for a typical two-unit flat.
Flex Duct Repair
Flex duct is common in Mission District crawl spaces because it’s the only material that can navigate the tortured geometry of retrofitted floor joist bays. It’s also what rats chew through first. We recently sealed a flex duct leak in a 1910 Edwardian flat on Capp Street where rats had chewed through the insulated lining, dumping drywall dust from a prior renovation into the bedroom supply. We cut out the damaged section, installed a new Rotobrush-compatible metal sleeve, and coated all joints with Guardsman mastic to prevent re-entry. Flex duct repair in Mission District typically runs $320-$480, including materials and the camera-verified finish.
Metal Duct Repair
When original galvanized ductwork in a Mission Victorian has corroded through from interior condensation, or when some prior owner’s DIY renovation crushed a supply run with a new wall, metal duct repair is the only lasting fix. We fabricate replacement sections on-site, match them to existing trunk lines, and secure them with proper slip joints and mastic. Metal duct repair in Mission District ranges from $380-$650 depending on accessibility and whether we need to enter through a crawl space on Shotwell or a basement hatch near Valencia.
Duct Insulation
The Mission sits in a fog-sheltered valley between Twin Peaks and Bernal Heights, making it one of San Francisco’s warmer, sunnier microclimates, but marine moisture still penetrates at night and through shoulder seasons. Older, poorly sealed retrofitted duct systems in these Victorian buildings are especially vulnerable to interior condensation and mold growth that residents in drier inland cities rarely encounter. We wrap exposed metal duct with formaldehyde-free insulation and seal the vapor barrier with mastic. Duct insulation in Mission District typically costs $340-$520 for a standard flat.
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 Mission District
We stock parts and specify equipment from Nikro, Honeywell, and Aprilaire, the same brands serious HVAC contractors use in commercial installations. For Mission District customers, that means we don’t need to special-order a metal sleeve or a particular mastic formulation and make you wait. Our van carries Rotobrush-compatible fittings, Guardsman mastic in multiple viscosities, and Honeywell duct board for on-site fabrication. Most repairs are completed in a single visit because we’ve already got what the job requires.
Common Duct Repair & Sealing Problems We See in Mission District Homes
- Rodent-gnawed flex ducts in unrenovated crawl spaces. The Mission District’s 100-year-old Victorian crawl spaces, combined with one of San Francisco’s densest urban rodent populations, create chronic duct damage from gnawed flex ducts and unsealed joints that require specialized mastic and metal repair rather than simple tape or sealant. Technicians cleaning ducts in Mission District Victorians routinely pull out nesting material, droppings, and even carcasses.
- Condensation inside uninsulated metal ducts. Marine moisture penetrates Mission District buildings at night, and retrofitted metal ducts running through floor joist bays collect condensation that leads to mold and corrosion. Duct insulation and mastic sealing together solve this.
- Illegally tapped or crushed duct runs from decades of DIY renovations. Small Mission flats have seen repeated renovations, and previous owners often tapped new supplies off existing runs or crushed ducts with new walls. These pressure imbalances require full metal duct repair to restore proper airflow.
- Drywall dust and demolition particulate from gentrification-era gut renovations. The neighborhood’s successive waves of renovation have loaded old ducts with debris that accumulates far beyond what a filter change can address, accelerating wear on joints and seals.
Pricing for Duct Repair & Sealing in Mission District, CA
A typical duct sealing job in Mission District runs $280-$420. Flex duct repair is usually $320-$480. Metal duct repair, which requires more labor and fabrication, ranges $380-$650. Duct insulation for a standard flat costs $340-$520. What moves you within these ranges is accessibility, a crawl space on Capp Street with 18 inches of clearance takes longer than a basement near Valencia, and the extent of damage, whether we’re patching one joint or replacing a full run.
We disclose every dollar before we lift a tool. The number on the phone is the number on the invoice. We also honor our standing offers: $50 off any repair over $250, a free second opinion on any written estimate, and a permanent 5% senior and veteran discount. Call (844) 685-6342 for an exact quote. Estimates are free.
We Also Serve Cities Near Mission District
Our vans run regular routes to Mission District neighbors in Noe Valley, San Francisco proper, Chinatown, and Daly City. If you’re in one of these areas and your ducts need attention, the same live-answer phone line and same-day scheduling apply.
Serving Mission District, CA - Our Local Coverage Area
We’re based in the Mission District 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 Mission District
The combination of extremely dense urban rodent populations and abundant unrenovated 100-year-old crawl spaces beneath Victorian flats creates conditions rarely matched elsewhere in the city. Rats enter through unsealed duct joints at the subfloor level, gnaw through flex duct insulation, and nest in the debris-trapping dead zones of retrofitted duct runs. We repair this damage with metal sleeves and mastic-sealed joints that resist re-entry. Call (844) 685-6342 if you suspect rodent damage. Estimates are free.
Yes, in nearly all cases we access and repair ducts through existing crawl-space hatches, basement entries, or removable floor panels without disturbing finished walls or original fir flooring. Our technicians carry compact equipment specifically for Mission District’s tight clearances. Call (844) 685-6342 to schedule an inspection. Estimates are free.
We use high-viscosity Guardsman mastic applied by brush to all joints and penetrations, then verify with a pressure test. The irregular geometry of these retrofitted runs makes tape and spray foam unreliable. Mastic remains flexible and maintains its seal through thermal expansion and vibration. A typical mastic sealing job in Mission District runs $280-$420. Call (844) 685-6342 for a specific quote. Estimates are free.
Yes, proper duct insulation with a sealed vapor barrier is the most effective solution for condensation in Mission District’s marine-influenced climate. We wrap exposed metal duct with formaldehyde-free insulation and seal all seams with mastic to prevent moisture contact with the metal surface. Duct insulation in Mission District typically costs $340-$520. Call (844) 685-6342 to discuss your situation. Estimates are free.
We often install metal sleeves at critical junction points and transition to metal where flex has been repeatedly damaged, while preserving flex only where its flexibility is genuinely needed to navigate tight joist bays. This hybrid approach solves the rodent problem without forcing unnecessary demolition. Flex duct repair with metal reinforcement in Mission District typically runs $320-$480. Call (844) 685-6342 for an assessment. Estimates are free.
Ready to stop losing heated air into your crawl space and start breathing clean again? Call Bellows Air Duct & Vent Co. at (844) 685-6342. We’ll answer live, schedule your free estimate, and most repairs are finished in a single visit. The 90-Day Done Right Promise applies to every job, and Ray Castillo stands behind it personally.
Written by Ray Castillo, Owner at Bellows Air Duct & Vent Co., serving Mission District since 1984.