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 Repair & Sealing Across Sterling
Duct repair and sealing in Sterling, VA typically runs $280-$720 for most residential jobs, with flex duct replacement in the Cascades area often landing in the $450-$620 range due to longer run configurations. We dispatch crews to Sterling daily from our Washington, DC coordination office, and most Sterling homeowners get a written estimate within 24 hours of calling. If you’re in the Cascades subdivision, Sterling Park, or Countryside and your upstairs registers barely move air, the problem is usually not your blower motor - it’s what’s happening inside the duct runs themselves.
Call (571) 520-6317 for a free written estimate. We answer live, 24/7.
Why CleanRun Air Duct Cleaning Herndon Is Sterling’s Preferred Duct Repair & Sealing Company
We’ve been documenting the inside of Sterling ductwork since 2013. That photo record - before and after every run - is included on every job, no exceptions. It started because we were tired of an industry that sold vacuum noise and called it clean. Now it’s Haven Standard Clause 2: Documented Evidence.
Sterling homeowners specifically hire us because we’ve seen what their homes contain. In Cascades, we regularly find flex duct runs sized for construction speed, not airflow, sagging at the elbows where drywall dust from 2003 still sits. In Sterling Park, we pull apart duct board systems from the 1970s where the interior liner has degraded into fiberglass particulate. We don’t guess. We photograph it, show you, and write the price before touching a tool.
Our technicians are background-checked, uniformed, and identified by name before arrival - Haven Standard Clause 3: Verified Crews. Every job carries the 365-Day Done Right Promise in writing. If it’s not right, we make it right. No manager approval required. The promise is printed on your job record, not just our website.
We also offer a Free Second Opinion on any written estimate from another company. Bring us their number. We’ll put ours next to it in writing. No charge.
Our Duct Repair & Sealing Services in Sterling
Flex Duct Repair
Sterling’s Cascades homes were built with some of the longest flex duct runs in Loudoun County. Two-story colonials with remote second-floor zones require 30-foot-plus spans with multiple bends. Over time, these sag. Joints separate. The wire helix inside kinks. We replace collapsed sections with properly supported flex duct sized to the CFM load, not whatever was left on the truck in 2003. In a recent Cascades job on Algonkian Parkway, our crew found two separated joints above a first-floor ceiling that had been dumping conditioned air into the joist bay for years. The homeowner’s “failing AC” was actually a duct problem. We repaired the runs, sealed with mastic, and the system static pressure dropped 0.3 inches.
Mastic Sealant Application
Tape fails. Mastic doesn’t. We apply professional-grade mastic sealant to every joint, seam, and penetration in your duct system, including the plenum - that’s the big distribution box attached to your air handler - and all branch connections. In Sterling’s older Sterling Park homes, we’ve found original tape turned to powder after 40 summers. Our mastic application is brushed on thick, rated for the temperature swings your attic or crawlspace sees through a Dulles-corridor winter. The result is measured: we run a duct blaster or pressure pan test to verify leakage reduction before we leave.
Air Leak Repair
Air leaks in Sterling homes fall into patterns. Newer Cascades builds leak at the register boot connections where flex meets the drywall. Older Countryside townhomes leak at the plenum seams and at filter rack gaps. We don’t just seal what we can reach. We pressurize the system, use smoke pencils or theatrical fog to find the leaks you can’t see, then repair each one with appropriate materials - mastic for rigid duct, proper mechanical fasteners for flex, and sealed access panels where we had to cut in. Every repair location is photographed before and after.
Metal Duct Repair
Some Sterling homes, particularly early Sterling Park split-levels and a few Countryside builds, used galvanized metal trunk lines with fiberglass-lined interiors. When that liner degrades, it sheds into your airflow. We repair or replace damaged metal sections, re-line where appropriate with closed-cell insulation that won’t degrade, and seal all seams with mastic. Metal work costs more than flex - typically $380-$850 in Sterling - but it lasts. We quote it in writing before starting.
Duct Insulation
Uninsulated or poorly insulated ductwork in Sterling crawlspaces and attics bleeds energy. In summer, your cold supply lines sweat in humid crawlspaces, creating condensation that feeds mold. In winter, heat loss to an unconditioned attic means your furnace works harder for the same result. We install proper R-8 insulation on replacement flex runs and wrap accessible metal with foil-faced fiberglass. The work is photographed and included in your job record.
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.
BeforeAfterTrusted Brands We Service in Sterling
Our equipment roster includes Rotobrush for mechanical agitation in flex runs, Nikro for negative-pressure extraction systems, and Honeywell media filters and zoning controls we install when a repair reveals the original system was never properly equipped. We don’t buy no-name tools. You can look up every brand we use. Parts for common Sterling HVAC configurations - Carrier, Trane, Lennox, Rheem - are stocked or sourced with next-day availability through our Washington, DC office coordination. No waiting two weeks for a proprietary fitting.
Common Duct Repair & Sealing Problems We See in Sterling Homes
- Construction debris baked into flex runs since handover. In Cascades, we regularly open duct systems that have carried drywall dust and wood particulate since the builder’s crew packed up. The debris doesn’t stay put - it migrates to elbows and damper boxes, restricting airflow and degrading indoor air quality. Source removal under negative pressure, followed by repair of any damage the debris caused, is the only fix.
- Sagging flex duct at multi-bend configurations. Long runs with three or more bends trap debris at each turn and create static pressure losses the HVAC system was never designed to overcome. The flex literally collapses at the kink. We replace with properly supported runs, maximum 90-degree bends, and metal elbows where turns are unavoidable.
- Duct board liner degradation in Sterling Park-era homes. Fiberglass duct board from the 1970s and 80s has an interior coating that breaks down after decades of humidity cycling. The surface becomes friable - that means it crumbles on contact - and the fibers enter your airflow. We replace with modern flex or metal where accessible, or line with closed-cell insulation where replacement isn’t feasible.
- Disconnected joints dumping conditioned air into building cavities. This is the silent efficiency killer. Your blower runs longer. Your bills climb. The house never quite cools or heats evenly. We find these with pressure testing and seal them properly, not with tape that’ll fail in two seasons.
Pricing for Duct Repair & Sealing in Sterling, VA
Here’s what duct repair and sealing actually costs in Sterling’s market. These are whole-system or per-project ranges, agreed in writing before work starts. No per-vent pricing. No teaser rates that balloon once we’re on site.
| Service | Typical Range in Sterling |
|---|---|
| Basic air leak sealing (mastic, accessible joints) | $280-$420 |
| Flex duct repair / section replacement (1-2 runs) | $340-$580 |
| Extensive flex replacement (Cascades-style long runs) | $450-$720 |
| Metal duct repair / re-lining | $380-$850 |
| Duct insulation (attic or crawlspace wrap) | $320-$640 |
| Full system diagnostic with photo documentation | $0 (included with any repair) |
What moves you within these ranges: accessibility (crawlspace vs. finished basement), number of runs, and whether we find construction debris that requires source removal before sealing. We photograph everything, explain what we found, and write the exact price before any work begins. Haven Standard Clause 1. No exceptions.
Call (571) 520-6317 for your free written estimate.
We Also Serve Cities Near Sterling
Our Duct Repair & Sealing crews work throughout Loudoun and Fairfax counties. We regularly repair ducts in Sterling, Herndon, Reston, Chantilly, and Leesburg. Same written pricing, same photo documentation, same 365-Day Done Right Promise in every city.
Serving Sterling, VA - Our Local Coverage Area
We’re based in the Sterling 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 Sterling
Builder-installed flex duct in Sterling’s newer homes, especially Cascades builds from the late 1990s through early 2000s, was often sized for speed of installation, not long-term airflow performance. Drywall dust and construction debris frequently remains in the system at handover, accelerating joint separation and sagging. We recommend a camera inspection within the first five years. Call (571) 520-6317 to schedule - estimates are free.
Cascades homes feature long, multi-bend flex runs serving two-story floor plans with secondary-zone dampers that trap debris where hands can’t reach. Sterling Park homes use older duct board or early flex that has simply aged past service life, with liner degradation and mold in crawlspaces from decades of Dulles-corridor humidity. The repair approach differs: Cascades needs strategic re-routing and damper box access; Sterling Park often needs full material replacement. We assess and quote each specifically.
We pressurize the system and measure static pressure at the air handler and at each register. A significant pressure drop between the plenum and a distant register indicates a disconnection, crush, or severe blockage. We confirm with a camera inspection inside the run, photograph the damage, and show you before proposing repair. No guesswork. Call (571) 520-6317 for a diagnostic.
Yes. Sterling sits in the Dulles Airport corridor where July dew points regularly hit the low 70s and attic temperatures exceed 130°F. This humidity migrates into any duct leak, condenses on cool supply surfaces, and creates mold-friendly conditions. Sealing leaks isn’t just an efficiency measure here - it’s moisture control. We see more mold-positive duct systems in Sterling than in drier western Loudoun County.
Sealing improves any system, but 1990s flex duct has exceeded its 20-25 year service life. The inner liner degrades, the wire helix fatigues, and the insulation compresses. We seal what we can access, document the condition of inaccessible runs with photos, and give you a written assessment of what needs replacement now versus what can wait. No pressure. Just evidence.
Written by Tomas Reyes, Owner at CleanRun Duct Repair & Cleaning, serving Sterling and Loudoun County since 2013.