Duct Repair & Sealing Cost - Leakage Measured, Then Priced in Writing

Every visit starts with

Whole-system duct and dryer vent check with before-and-after photos - you see exactly what came out of your vents

Worth knowing

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.

Styles & brands we work with

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Before & after – our own jobs

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How Much Does Duct Repair & Sealing Cost in Herndon?

Our Duct Repair & Sealing services in Herndon, VA typically cost between $350 and $1,200 for a standard single-family home, with most jobs landing in the $450-$800 range depending on access, the number of breached duct runs, and whether aerosol sealing or hand-applied mastic is used. Jobs that require plenum repair – the main distribution box that feeds all your supply runs – or that involve inaccessible ductwork above finished ceilings will sit closer to the top of that range. At CleanRun, every price is written before any panel comes off, so there are no revisions once work begins.

Duct Repair & Sealing Cost Breakdown (2026)

The table below reflects actual pricing in the Herndon market as of 2026. Northern Virginia carries higher labor costs than the broader DMV average, and Herndon’s mix of 1970s-1990s townhomes, newer Dulles corridor subdivisions, and older flex-space conversions means ductwork configurations vary considerably from address to address.

A few things move these numbers. Homes in Herndon’s older Sycamore Street corridor and the neighborhoods around Worldgate tend to have original galvanized steel duct runs that seal well with hand-applied mastic because the duct walls are rigid and joints are accessible. Newer construction near Herndon Parkway and the Innovation Center area often uses flex duct, which is more prone to disconnection at the collar but also faster to reattach when the connection is fully exposed. Where ductwork runs through finished walls or above drywall ceilings – as it does in many of the stacked townhomes off Elden Street – access becomes the dominant cost driver, not materials.

At CleanRun, the written price you receive before any work starts reflects the specific duct configuration photographed during the assessment, not a generic estimate. Haven Standard Clause 1 means the number on paper is the number on the invoice.

What Affects Duct Repair & Sealing Pricing in Herndon

• Duct material and age: Herndon has significant housing stock from the late 1970s through the early 1990s, and a lot of that ductwork is original. Older fiberglass duct board deteriorates at the seams and sometimes at the inner liner, which means repair costs more than simply sealing a metal joint. If the duct board has softened or collapsed – something our camera shows clearly before we quote anything – replacement is the right call, not additional sealant layered over a compromised substrate.
• Number of leakage points: A single disconnected flex joint is a 45-minute repair. A system that failed a duct blaster test at 25% leakage across eight runs is a full-day job. The camera assessment identifies every breach point and that count is what drives the written scope.
• Access conditions: Crawlspace work in Herndon requires working in tight, sometimes damp conditions – especially in the older sections of the Herndon Historic District where crawlspaces can be under 30 inches. Attic work in July, where temperatures exceed 140°F, carries a legitimate access surcharge. Both conditions appear on your written quote with the specific add-on itemized, not rolled into a vague “labor fee.”
• Sealing method – mastic vs. aerosol: Mastic (a fiber-reinforced paste applied by hand) and foil-backed tape are the right tools for accessible joints. Aerosol injection – where a pressurized mist of sealant particles is circulated through the pressurized duct system and bonds to leakage points from the inside – costs considerably more but reaches locations that no technician’s hand can reach. Most Herndon homes need mastic work. A subset of homes with complex above-drywall runs benefit from the aerosol method, and we’ll tell you which applies to your system before you decide.
• Combo scope vs. repair-only: If your ductwork also needs cleaning, scheduling both services on the same visit reduces total labor time compared to two separate mobilizations. The savings aren’t dramatic – typically $75 to $150 – but they’re real and they’ll appear as a line-item credit on the written quote.
• Northern Virginia regional labor rates: Herndon sits in Fairfax County, one of the higher labor-cost markets in Virginia. Skilled sheet-metal and HVAC duct technicians in this area command rates that are meaningfully higher than central Virginia or the Shenandoah markets. That’s reflected in our pricing and it’s reflected in every competitor’s pricing, whether they show it to you upfront or not.

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Signs You Have a Duct Leak – What the Camera Actually Shows

Most homeowners in Herndon discover a duct problem through a symptom – a room that won’t cool, an energy bill that jumped $60 to $90 in a single billing cycle, or visible dust rings on the ceiling around a supply register. Those are real indicators, but they don’t tell you where the leak is or how bad it is. The camera does.

In Herndon homes built between 1978 and 1995, we see a consistent pattern at the first elbow off the plenum: the duct tape used in original construction has dried out and pulled away from the sheet-metal collar, leaving a gap that can measure anywhere from a quarter-inch to more than two inches around the circumference. That gap alone can push 15-20% of conditioned air into the attic or crawlspace rather than into the room the run is supposed to serve. The camera photographs it. The written scope names it. The mastic seals it. And the post-work photograph documents that it’s closed.

In newer flex-duct systems – common in developments built along the Dulles corridor in the early 2000s – the failure mode is usually at the inner liner rather than the outer jacket. The outer sleeve looks intact from a visual inspection, but the inner liner has pulled away from the collar, and conditioned air is bleeding into the interstitial space between the two layers. That’s invisible to the eye but not to a camera probe. This is one of the reasons CleanRun has photographed the inside of every duct run on every job since 2013: the camera finds what a flashlight and a mirror miss.

The CleanRun Pricing Process – Written Before Any Work Starts

The standard service model in the Herndon HVAC and ductwork industry has a problem: too many companies quote a low number to get in the door, then identify “additional needs” once the equipment is set up and the homeowner is three steps into a commitment. CleanRun was built as a direct answer to that model. Haven Standard Clause 1 is not a marketing line – it is the operating rule under which every job at every address is run. The technician photographs the system, identifies every repair point, and puts a written dollar figure in front of you before touching a single duct.

If the scope changes after work begins – which is rare, but sometimes the camera reveals a secondary breach behind a repaired section – the job stops, you see the new photograph, and you approve a revised written price. The work does not continue on assumption.

Tomas Reyes built CleanRun on this model because the written price is the only version that holds a company accountable. A verbal estimate cannot be disputed. A written price can be.

Duct Repair & Sealing vs. Full Duct Replacement – When Repair Makes Sense

This question comes up on roughly one in four assessments in Herndon. The short answer: repair and sealing makes sense when the duct material itself is structurally sound and the leakage is limited to joints, collars, and seams. Full replacement makes more sense when the duct board has collapsed, when flex duct has kinked in multiple locations reducing airflow by 30% or more, or when a system is undersized for a home that has been expanded since original construction.

At current Herndon material and labor rates, a full duct replacement on a 2,200 square foot single-family home runs $2,800 to $5,500 depending on duct type, access, and whether the air handler needs repositioning. Repair and sealing on the same home, if the ductwork is structurally sound, runs $500 to $900. Those numbers are far enough apart that the repair-vs.-replace decision is worth making carefully, with camera documentation in hand, not from a verbal description of what a technician “saw.”

CleanRun’s assessments photograph the condition before any recommendation is made. If the camera shows intact duct board with sealed joints, we say so – and we say it in writing. If it shows collapsed liner and deteriorated fiberglass throughout, that shows up in the photo record too. The evidence drives the recommendation, not the other way around.

How to Save on Duct Repair & Sealing in Herndon

The most practical ways to reduce cost on duct repair are also the most straightforward. They don’t require special negotiation or waiting for a seasonal promotion.

• Get a written price from more than one company. CleanRun offers a free second opinion on any written estimate – bring a competitor’s quote and we’ll put our own number next to it in writing, line by line. This costs you nothing and gives you a documented basis for comparison rather than two verbal numbers you’re trying to hold in your head.
• Combine duct repair with duct cleaning if your system needs both. Scheduling on one visit reduces total mobilization cost. The combined scope also makes more sense from an air quality standpoint – sealing a dirty duct system locks debris in place, while cleaning before sealing gives you a system that starts clean and stays sealed.
• Address small repairs before they become large ones. A single disconnected flex collar repaired today costs roughly $75-$140. Left for two heating seasons, that gap allows moisture infiltration in Herndon’s humid summers, which can degrade adjacent duct board and create a repair scope that costs four to six times as much.
• Verify your scope against the camera footage. Every CleanRun job includes a before-and-after photo record. If a competitor quotes a repair and cannot show you a photograph of the breach they’re repairing, that’s a meaningful gap in accountability – and it often means you’re paying for repairs that may or may not have happened.
• Use your written estimate to check for scope creep. Any company – including CleanRun – should be able to show you the written price from before work started and the invoice after, and explain any difference in writing. If those two documents don’t match and no revised written approval exists, you’ve encountered scope creep. The written price process eliminates this risk entirely on CleanRun jobs.

For a written price on your Herndon home’s duct system, call (571) 520-6317. The estimate is free, the price is written, and it doesn’t change once work begins.

What the 365-Day Done Right Promise Covers on Duct Repair Jobs

Most duct repair warranties in the Herndon market are verbal or buried in fine print that limits the coverage to 30 or 90 days. CleanRun’s 365-Day Done Right Promise is a written guarantee on every job: if the repair is not right – if a sealed joint reopens, if mastic fails at a joint that was in the documented scope, if a reattached flex collar pulls loose – CleanRun returns and corrects it at no additional charge. The guarantee is in writing on the job record, not subject to manager review or conditional on circumstances not defined at the time of service.

The 365-day window reflects the fact that duct systems go through a full annual cycle of expansion and contraction. A seal that holds through a Virginia summer and a Northern Virginia winter has genuinely held. That’s the test CleanRun’s work is designed to pass.

Herndon-Specific Notes on Duct Repair Costs

Herndon’s housing inventory creates a few patterns worth knowing before you contact any duct repair company in town.

Homes in the Chandon and Fox Mill Station neighborhoods, built largely in the late 1980s and early 1990s, often have two-zone systems where the ductwork branches at a secondary plenum in the attic. That secondary plenum is frequently the first place joints fail because it carries less support than the main trunk. Repair here typically requires attic access, which adds to the job scope.

Townhomes along Elden Street and near the Herndon Metro station tend to have ductwork routed through interior walls to serve upper floors. Those runs are inaccessible without opening drywall, which is why aerosol injection is sometimes the only practical sealing method for leaks in those sections. The base aerosol price range of $900-$1,800 reflects this specifically.

Properties in the older parts of Herndon near the historic downtown – particularly homes built before 1980 – sometimes have duct runs lined with a material that was discontinued for residential use. Camera assessment identifies this condition immediately, and the scope in those cases shifts from sealing to a discussion about encapsulation or section-by-section replacement. We’ll tell you exactly what the camera shows before any price is discussed.

The Duct Repair & Sealing in Herndon service page covers the full technical scope of what each repair type involves if you want to understand the work before calling. And if you’re trying to understand how duct work fits into the broader picture of air quality and HVAC performance in your home, the CleanRun home page outlines all the services we document and guarantee.

FAQs – Duct Repair & Sealing Cost in Herndon

How much does duct sealing cost in Herndon, VA?

Duct sealing in Herndon costs $450 to $850 for most single-family homes in the 1,800-2,800 sq ft range using hand-applied mastic or foil-backed tape on accessible runs. Aerosol injection for inaccessible leaks runs $900 to $1,800. The exact number depends on how many breach points the camera identifies and how accessible those points are. Call (571) 520-6317 for a written price specific to your address – the estimate is free.

Is duct repair worth it, or should I replace the ductwork?

Repair is worth it when the duct material is structurally intact and leakage is limited to joints and seams – which is the case in the majority of Herndon homes we assess. Full replacement, which runs $2,800 to $5,500 on a typical Herndon home, makes sense when duct board has collapsed, flex duct has kinked significantly in multiple places, or the system is undersized for the current square footage. The camera assessment gives you the evidence to make that call with confidence rather than guessing. Call (571) 520-6317 and we’ll photograph the system and put the recommendation in writing before quoting either path.

How long does duct sealing take?

A standard hand-mastic sealing job on 8-12 runs in a Herndon single-family home takes 3 to 5 hours including the pre-work camera documentation and post-work photography. Aerosol injection adds time for system pressurization and sealant curing – typically a full day visit. Attic or crawlspace work can extend the timeline depending on access conditions. The written scope you receive before work starts will include an estimated time frame.

Can I seal ductwork myself to save money?

Accessible joints in an unconditioned basement or crawlspace can be treated with UL-listed foil-backed tape or mastic by a capable DIYer – and for a single loose joint that’s visible and reachable, that’s a reasonable option. The problem is diagnosis: without a camera, you’re sealing what you can see, not necessarily what’s leaking. In Herndon homes with attic or wall-routed ductwork, the leakage points are almost never the ones visible from the basement. Sealing accessible joints while leaving inaccessible breaches open gives you the cost of a repair without the benefit of one. Call (571) 520-6317 and we’ll photograph the system first so you know what you’re actually dealing with before deciding how to address it.

Does CleanRun charge for the estimate?

No. The estimate is free, and it comes with a written price – not a range, not a verbal ballpark. Haven Standard Clause 1 means no work begins until the written price is in front of you and you’ve approved it. If you have a written quote from another Herndon duct repair company, bring it: CleanRun’s free second opinion puts our number next to theirs in writing, line by line. Call (571) 520-6317 to schedule.

What warranty comes with duct repair in Herndon?

CleanRun backs every duct repair with the 365-Day Done Right Promise – a written guarantee, documented on the job record, that covers any failure within the repaired scope for a full calendar year. If a sealed joint opens or a reattached flex collar fails within 365 days of the job, CleanRun returns and corrects it at no charge. The guarantee is written, not verbal, and it doesn’t require manager approval to activate. No other duct repair company in the Herndon area publicly documents this commitment at that duration.

Tomas Reyes leads CleanRun Air Duct Cleaning Herndon, independently owned and operated under the Haven Standard since 2013. CleanRun has served over 52,000 homes across Northern Virginia, every one with a written price before work began and a documented photo record when the crew left. Background-checked, uniformed technicians use professional-grade equipment from Rotobrush, Nikro, Abatement Technologies, Honeywell, Aprilaire, and Guardsman on every job.

Pricing reflects the Herndon, VA market as of 2026. CleanRun Air Duct Cleaning Herndon offers free estimates – call (571) 520-6317.

Written by Tomas Reyes, Owner at CleanRun Air Duct Cleaning Herndon, serving Herndon since 2013.