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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Before
AfterFast, Reliable Duct Repair & Sealing Across Fairfax
Duct repair and sealing in Fairfax typically runs $340-$1,200 depending on whether the job involves sealing accessible joints or replacing delaminated liner in aging systems. Most Fairfax homeowners call us after noticing uneven temperatures between floors, musty odors when the AC cycles on, or energy bills that climb every humid summer without explanation. Our crews are dispatched from our Washington, DC scheduling office and carry Nikro negative-pressure extractors, Honeywell media, and Guardsman mastic compounds on every Fairfax route. If your home sits in Mantua, Greenfield, or any of the 1960s-1980s neighborhoods that make up Fairfax’s core housing stock, the ductwork is likely 40-60 years old and was built for a climate-control standard that predates modern efficiency codes. Call (240) 255-4519 for a written estimate before any work starts.
Why CleanRun Air Duct Cleaning Rockville Is Fairfax’s Preferred Duct Repair & Sealing Company
We’ve served Fairfax since adding the county to our regular routing in 2013, and the photo records from those early jobs show the same patterns we find today: original fiberglass duct liner delaminating inside sheet-metal shells, flex joints in unconditioned attics sweating through July and August, and return plenums pulling attic air through gaps a homeowner would never see without a camera. Our Duct Repair & Sealing crews have documented these conditions in more than 3,800 Fairfax homes, every visit ending with a written price, a photo record of every duct run, and the 365-Day Done Right Promise backed in writing under Haven Standard Clause 1.
Fairfax customers find us because they have already received a fogging “sanitiser” quote from another company and want to know why the smell keeps coming back. We explain what the camera showed: delaminated liner, not surface mold. Then we show them the photo. That difference - evidence before persuasion - is why our Fairfax referral rate runs higher than our other service corridors.
Technicians are background-checked, uniformed, and identified by name before arrival under Haven Standard Clause 3: Verified Crews. Scheduling is coordinated from our Washington, DC office, with Fairfax routes planned to minimize transit time and keep appointment windows tight. Every call is answered by a live person, 24/7.
Our Duct Repair & Sealing Services in Fairfax
Duct Sealing
Unsealed duct joints in Fairfax’s older homes waste 20-30% of conditioned air into attics and crawlspaces, according to Department of Energy estimates we’ve verified in field testing across Mantua and Greenfield properties. Our sealing protocol applies mastic sealant - a fiber-reinforced compound that remains flexible across temperature swings - at every boot, joint, and plenum connection, then verifies closure with a pressure test. A typical duct sealing scope in Fairfax runs $340-$680 for a single-system home. We do not quote per-vent pricing; the written price covers the whole system, agreed before the first panel comes off.
Flex Duct Repair
Fairfax’s high summer humidity attacks flex duct at its weakest points: the crimped connections to metal trunk lines and the sagging runs in unconditioned attic spaces where dew points in the low 70s condense on the outer jacket. We replace compromised flex with new insulated runs, support them to eliminate sag, and seal every transition with mastic. A partial flex replacement in Fairfax typically costs $280-$560 per run, with full-system replacements in larger colonials reaching $890-$1,400.
Metal Duct Repair
The sheet-metal trunk lines in Fairfax’s 1960s-1980s colonials were built to last, but the internal fiberglass liner was not. When our camera shows delamination - liner sagging off the metal in sheets, as we documented on a 1962 split-level off Barkley Drive in Mantua - the repair pivots from cleaning to liner removal and reline. We strip the failed liner, clean the metal shell, and apply a new internal coating or replace the affected section entirely. Metal duct repair with liner replacement in Fairfax ranges from $560-$1,200 depending on linear footage and accessibility.
Duct Insulation
Uninsulated or poorly insulated supply runs in Fairfax attics sweat through the cooling season, creating the moisture that feeds mold inside the duct and rust on the metal. We install new fiberglass or foil-faced insulation at R-6 or R-8 values, sealed at every seam, to keep the duct surface above dew point even when Fairfax humidity pushes past 70%. Duct insulation work in Fairfax typically runs $450-$920 for a standard colonial with attic trunk lines.
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.
Before
AfterTrusted Brands We Service in Fairfax
Our Fairfax trucks stock Honeywell media filters, Aprilaire humidifier and dehumidifier components, and Abatement Technologies HEPA filtration equipment - parts we can source same-day for most Fairfax jobs without waiting on regional distribution. When a repair requires replacement components rather than sealing or relining, we specify the manufacturer and model number in writing before ordering, so you can verify specifications independently. We do not install generic “compatible” parts in duct systems; the Haven Standard requires brand-documented components on every repair.
Common Duct Repair & Sealing Problems We See in Fairfax Homes
- Delaminated fiberglass liner in original ductwork. In Mantua and Greenfield homes built before 1970, we routinely find liner that has separated from the sheet-metal shell, shedding particulates into the airstream and creating hollow spaces where mold colonizes. A brush-and-vacuum cleaning cannot fix this; the liner must be removed and the run relined or replaced.
- Condensation at uninsulated flex joints in attics. Fairfax’s summer dew points in the mid-60s to low-70s °F hit uninsulated flex connections hard, producing water stains on ceiling drywall below and musty odors when the system cycles. Sealing without insulating the joint just moves the condensation point.
- Return plenums drawing attic air through gaps. The multi-branch duct runs in Fairfax’s split-levels and colonials often feature return plenums with unsealed access panels or degraded gaskets, pulling hot, humid attic air into the system and overloading the AC with latent moisture.
- Fogging “sanitiser” residue masking deeper failure. We’ve opened ducts in Fairfax homes that received a $79 fogging treatment six months prior; the chemical scent had faded, but the delaminated liner and active mold remained. Fogging does not remove source material. It perfumes it.
Pricing for Duct Repair & Sealing in Fairfax, VA
Honest pricing means naming numbers before you commit, not after we’re in your basement. Here is what duct repair and sealing costs in Fairfax’s market as of 2025:
| Service | Fairfax Price Range |
|---|---|
| Duct sealing (mastic, whole system) | $340 - $680 |
| Flex duct repair / replacement (per run) | $280 - $560 |
| Metal duct repair with liner removal | $560 - $1,200 |
| Duct insulation (attic trunk lines) | $450 - $920 |
| Full system assessment with photo record | Included free with any repair scope |
These ranges reflect Fairfax’s housing stock - older, multi-branch systems in unconditioned spaces that require more labor than newer, compact duct layouts. A 2,400-square-foot colonial in Mantua with attic and crawlspace runs will land higher in these ranges than a smaller rambler with basement ductwork. We deliver a written price before any work starts, every time, under Haven Standard Clause 1. No exceptions. Bring a competitor’s written estimate and we’ll provide a Free Second Opinion, our number next to theirs.
We Also Serve Cities Near Fairfax
Our crews route regularly through Fairfax, Reston, Herndon, Sterling, and Arlington from our Washington, DC dispatch office. The ductwork patterns differ by city: Reston’s 1980s-90s construction shows less liner delamination but more flex-duct sag from longer attic runs; Herndon’s townhome clusters present compact systems with different access challenges. We adjust our scope and pricing to what the home actually needs, not what a regional template assumes.
Serving Fairfax, VA - Our Local Coverage Area
We’re based in the Fairfax 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 Fairfax
Fairfax’s Mantua and Greenfield subdivisions were built in the 1950s-1960s with fiberglass-lined sheet-metal ductwork that is now 60-plus years old, and the Mid-Atlantic’s summer humidity - regularly above 70% relative humidity from June through September - accelerates moisture infiltration and mold colonization inside this aging material. Newer Reston construction from the 1980s onward typically uses unlined metal or properly insulated flex duct that does not trap moisture the same way. The delaminated liner in Mantua homes is a source-removal job, not a surface treatment. Call (240) 255-4519 for an exact quote - estimates are free.
No. Fogging deposits a chemical coating on surfaces but does not remove the delaminated fiberglass duct liner, accumulated debris, or active mold colonies that are the actual source of the problem in Fairfax’s older homes. Once summer dew points climb back into the low 70s, moisture reactivates growth on the remaining material and the smell returns within weeks. We have documented this cycle in dozens of Fairfax photo records: fogged ducts with clean-smelling residue over intact mold colonies. Genuine repair requires source removal, then sealing or relining to prevent recurrence. Call (240) 255-4519 for an exact quote - estimates are free.
We run a camera through every accessible duct run and photograph the interior condition; sealing is appropriate when the metal or flex is structurally sound with gaps at joints or boots, while repair or replacement is required when we find delaminated liner, corroded metal, or collapsed flex. In a 1962 split-level off Mantua’s Barkley Drive, our tech pulled a supply register and found the original fiberglass liner sagging off the sheet metal in sheets, with dew-point condensation already darkening the flex joint at the air handler. We switched from a standard source-removal clean to liner removal, applied mastic sealant at every unsealed boot and joint, and relined the run; the homeowner’s recurring musty smell in the upstairs bedrooms cleared in the first cooling cycle after the job. The photo record showed the difference. Call (240) 255-4519 for an exact quote - estimates are free.
Mold returns because the moisture source was never corrected. In Fairfax, that source is almost always condensation at uninsulated flex joints or inside unlined metal runs in humid attics and crawlspaces, combined with air leaks that pull humid outdoor air into the system. A standard brush-and-vacuum cleaning removes visible growth but leaves the thermal bridge that produces new condensation every summer. Our repair protocol seals the leaks, insulates the runs, and verifies with pressure testing that the system is no longer drawing unconditioned air. Without that step, the mold returns. Call (240) 255-4519 for an exact quote - estimates are free.
Yes. Fairfax’s older colonials and split-levels often have laundry rooms with dryer vents routed through long, convoluted pathways to exterior walls, creating lint accumulation that restricts airflow and creates a fire hazard independent of the HVAC duct system. This is a dryer vent cleaning issue, not a duct repair issue, though we frequently find both conditions in the same home. Our crews carry Nikro rotary brushes and HEPA vacuums for dryer vent work as a separate scope. Call (240) 255-4519 for an exact quote - estimates are free.
Ready to see what your ducts actually look like? We’ll run the camera, show you the photo record, and deliver a written price before any work starts. Every job is backed by the 365-Day Done Right Promise and documented with before-and-after photos of every duct run. Call CleanRun Air Duct Cleaning Rockville at (240) 255-4519 to schedule your free estimate.
Written by Tomas Reyes, Owner at CleanRun Air Duct Cleaning Rockville, serving Fairfax since 2013.