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 Thornton
Duct repair and sealing in Thornton, CO typically costs $340-$780 for most residential jobs, with full-system mastic sealing and flex-duct repair running at the higher end. Our crews are dispatched from our Denver office and carry the equipment to handle Thornton-specific problems: construction debris in new builds, industrial particulate loading in older neighborhoods, and the sagging flex-duct runs common north of 136th Avenue. Call (720) 799-2292 for a written estimate before any work starts.
We’ve worked in Thornton since 2013, and the housing stock here tells a clear story. Southern Thornton, roughly everything south of 120th Avenue, is packed with 1970s through 1990s tract homes built with fiberglass duct board that has rarely been opened. Northern Thornton, from 136th Avenue up past 144th, is filled with 2000s and 2010s production builds whose long flex-duct spans were strapped loosely and now sag between joists. Both zones need different approaches. Both get the same documentation: a written price before we touch anything, and a photo record of every duct run when we finish.
Why CleanRun Air Duct Cleaning Denver Is Thornton’s Preferred Duct Repair & Sealing Company
Our reputation in Thornton is built on what we can show, not what we claim. Every job since 2013 has started with a written price and ended with a documented photo record of every duct run, before and after. Homeowners here research before they call, and they stay customers because the evidence matches the promise.
We answer calls with a live person, 24/7, and our technicians are background-checked, uniformed, and identified by name before arrival, under Haven Standard Clause 3: Verified Crews. Scheduling is coordinated from our Denver office, but crews serve Thornton with local knowledge: which neighborhoods were built when, what contaminants to expect, and how Thornton’s semi-arid climate and industrial proximity change the work.
Our 365-Day Done Right Promise is backed in writing on every job, not buried in a policy manual. If the work is not right, we make it right. No manager approval required. The same guarantee covers our Duct Repair & Sealing work across the metro area.
Our Duct Repair & Sealing Services in Thornton
Duct Sealing
Leaky ducts in Thornton homes waste conditioned air into attics and crawl spaces, and the problem is worse here than in moister climates. At 5,350 feet with low humidity, Thornton’s dry air keeps dust particles light and mobile, so any gap in a duct joint becomes a two-way path: conditioned air escapes, unfiltered attic air gets pulled in. We seal with mastic compound and reinforced tape at every joint, boot, and plenum connection, then pressure-test to verify. A typical duct sealing job in Thornton runs $380-$620 for a single system, written before we start.
Flex Duct Repair
North Thornton homes near 136th-144th Avenue were built with long flex-duct runs that sag when support straps loosen. Low spots trap construction debris, drywall dust, and household particulate. They also kink and tear at bends. We re-support with proper hangers, replace damaged sections with new insulated flex, and seal every connection with mastic. Flex duct repair in Thornton typically costs $290-$540 per run, depending on accessibility and length.
Metal Duct Repair
Older Thornton homes and any with galvanized steel trunk lines need different handling. We see separated seams and rust-through in basements and crawl spaces, especially where humidity from evaporator coils has collected. Our crews fabricate replacement sections on site, seal with mastic, and insulate where the original wrapping has degraded. Metal duct repair in Thornton runs $420-$780, with full trunk-line replacement at the upper end.
Duct Insulation
Uninsulated or poorly insulated ducts in Thornton’s attics lose efficiency fast. Summer attic temperatures here hit 140°F, and winter nights drop below zero. We install foil-faced fiberglass wrap or closed-cell foam where appropriate, sealed at every seam. Duct insulation in Thornton typically costs $2.80-$4.20 per linear foot, with full written scope before work begins.
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 Thornton
Our equipment roster includes Rotobrush agitation systems, Nikro HEPA negative-air machines, Honeywell media filters, and Aprilaire whole-home air cleaners. We stock common repair parts for Thornton jobs so we’re not waiting on a Denver warehouse run. For duct sealing, we use Guardsman mastic compounds and reinforced foil tape rated for the temperature swings Thornton’s attics see. You can look up every brand yourself; we name them so you can.
Common Duct Repair & Sealing Problems We See in Thornton Homes
- New-build handover contamination. Homes under two years old in Thornton, especially north of 136th Avenue, often contain more drywall dust, sawdust, and drywall-mud grit than 1990s resales. Builders’ rough cleans rarely reach the ductwork. The camera shows it; we document it.
- Industrial particulate loading in south Thornton. Southern Thornton neighborhoods near 84th-104th Avenue sit downwind of Commerce City’s industrial corridor. Our technicians regularly find a thin gray-black sooty residue stratified beneath standard household dust in return plenums and fiberglass duct board interiors. Rotary brush cleaning alone does not remove it.
- Sagging flex-duct low spots in north Thornton. The 2000s-2010s production builds north of 136th Avenue were strapped with inadequate support spacing. Runs dip between joists, trap debris, and leak at every joint and boot. Re-supporting and sealing is standard on these jobs.
- Wildfire smoke infiltration. June through September, Front Range wildfire smoke loads submicron particulates into Thornton duct systems. These particles penetrate deep into duct lining and require HEPA-rated negative-air extraction to address after the fire season passes.
Pricing for Duct Repair & Sealing in Thornton, CO
We publish ranges because Haven Standard Clause 1 requires a written price before any work starts. Here is what duct repair and sealing costs in Thornton:
| Service | Typical Range in Thornton |
|---|---|
| Duct sealing (mastic, full system) | $380-$620 |
| Flex duct repair (per run) | $290-$540 |
| Metal duct repair (seam/section) | $420-$780 |
| Duct insulation (per linear foot) | $2.80-$4.20 |
| Air leak repair (boot/joint) | $180-$340 |
| Mastic sealant application (partial system) | $260-$480 |
Factors that move the number: accessibility (crawl space vs. basement), contamination level requiring source removal before sealing, and whether the system needs re-supporting. Every estimate is free, written, and delivered before we touch a panel. Bring a competitor’s quote; under Haven Standard Clause 5, we provide a Free Second Opinion in writing at no cost.
We were called to a 2006 production build near 136th Avenue in north Thornton where the homeowner complained that every register blew a fine white powder for weeks after closing. Camera inspection showed the long flex-duct runs sagging between joists, trapping drywall dust and construction debris in low spots; we set up negative pressure with HEPA filtration, ran agitation tools and source removal through the supply and return ducts, then re-supported and mastic-sealed the collapsed runs. The blower motor amp draw dropped and the powder stopped on the first cycle.
We Also Serve Cities Near Thornton
Our crews work Duct Repair & Sealing in Thornton and the surrounding communities: Westminster to the west, Broomfield and Arvada to the northwest, and Aurora to the southeast. Scheduling is coordinated from our Denver office, with local dispatch to each area.
Serving Thornton, CO - Our Local Coverage Area
We’re based in the Thornton 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 Thornton
Because builders’ rough cleans almost never reach the ductwork, and the fine white powder you see at registers is typically drywall dust, sawdust, and drywall-mud grit left in supply and return ducts at handover. In Thornton, this is especially common in the 2000s-2010s production builds north of 136th Avenue, where long flex-duct runs sag and trap debris in low spots. A home under two years old can be dirtier than a 1990s resale. Call (720) 799-2292 for a camera inspection and written estimate.
It is a sooty industrial residue from Commerce City’s heavy industrial corridor, which migrates north into Thornton during southerly wind events and stratifies beneath ordinary household dust in fiberglass duct board and return plenums. This signature contamination is distinct from standard dust and is not found in Westminster or Northglenn builds at the same concentration. Rotary brush cleaning alone leaves it behind; source removal with HEPA negative-air extraction and subsequent sealing is required.
They need both. Sagging creates debris-trapping low spots and leaks conditioned air at every joint and boot. Cleaning without re-supporting and sealing means the problem returns. We re-support with proper hangers, replace damaged sections, and mastic-seal every connection. The written scope includes all three steps, with photos of each run before and after.
By sealing the envelope, not just cleaning it. Mastic sealing at every joint, boot, and plenum connection prevents unfiltered attic and return-air leakage from pulling in outside particulate. For wildfire smoke season, we recommend upgrading to a Honeywell or Aprilaire media filter rated for submicron particles, installed downstream of the repaired ductwork. The sealed system plus proper filtration is measurable: we pressure-test after sealing and document the improvement.
It changes measurable airflow and efficiency. We pressure-test before and after sealing, and homeowners typically see reduced blower motor amp draw, more even temperatures room-to-room, and lower utility bills. The Department of Energy estimates typical duct leakage at 20-30% of conditioned air; sealing that gap is not decorative. Every Thornton job includes the before-and-after pressure reading in the written job record.
Written by Tomas Reyes, Owner at CleanRun Air Duct Cleaning Denver, serving Thornton since 2013.