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.
Before
After
Before
After
Before
AfterFast, Reliable Duct Sealing Across Duvall
Duct sealing in Duvall typically runs $450 – $1,200 for a whole-house job depending on access, duct material, and how many leaks we find. Most Duvall homes take a half-day to full day to seal properly, and we give you a written price before any work starts. Call (361) 326-5060 for a free estimate.
We’ve been driving out to Duvall from our Seattle office long enough to know the difference between a dry-side suburb and a Snoqualmie Valley floor home. The crews that serve Duvall locally understand what 38 – 40 inches of annual rain does to crawlspace ductwork, why mouse nests show up in trunk lines after harvest season, and why a 1990s two-story build off NE 124th Street needs a different approach than a 1970s rancher near Big Rock Road. That local knowledge matters because duct sealing done without it fails within a season.
Our Duct Sealing team works on Duvall’s timeline, not ours. We arrive inside the quoted window, price the job in writing before touching anything, and leave the site clean. Every seal is covered by our 365-Day Done Right Promise – if it fails, we come back at no charge.
Why Hollis Air Duct Cleaning Is Duvall’s Preferred Duct Sealing Company
Hollis Air Duct Cleaning has built its reputation in Duvall the same way we have everywhere: show up, say what you’ll do, do it, and stand behind it for a year. We’re part of the Garrison Partners family, in business since 2004, and every Hollis location operates under The Garrison Standard – written prices, written guarantees, and technicians who follow The Garrison Code on every job.
Duvall homeowners call us back because the price they were quoted is the price on the invoice. No per-vent add-ons, no “we found another problem” upsells once the van is in the driveway. Our 365-Day Done Right Promise covers every duct sealing job in writing: if the seal fails within a year, we return and make it right at no charge, including a free second visit.
Our technicians are background-checked and uniformed. You’ll know who’s arriving before they knock. And when you call (361) 326-5060, a live person answers – no voicemail loops, no callback queues, no waiting until Monday.
We serve Duvall with the same professional-grade equipment we use on commercial jobs: Rotobrush rotary brush systems, Nikro negative-air machines, and sealing products from Abatement Technologies and Guardsman. These aren’t hardware-store tools, and we explain what each one does before we start.
Duct Insulation in Duvall
Duct Insulation in Duvall is often the missing piece after sealing, especially in homes with crawlspace or attic runs that sweat through our cool, damp winters. A sealed duct without proper insulation still loses conditioned air through the duct wall itself, and in Duvall’s humidity, uninsulated metal trunk lines condense moisture that reopens seams and breeds mold. We insulate with wrapped fiberglass or closed-cell foam depending on the run location, and we always price it separately from sealing so you know exactly what each layer costs.
A typical Duvall duct insulation job runs $300 – $800 for partial coverage of problem runs, or $800 – $1,800 for full-house wrap on older valley-floor homes with extensive metal trunk lines.
When Insulation Matters More Than Sealing Alone
Some Duvall homes we inspect have ducts that are technically sealed but hemorrhaging energy through thin, uninsulated walls. In a two-story build off Cherry Valley Road with long flexible runs to upstairs bedrooms, insulation often matters more than another round of mastic. We check every run with a thermal camera and tell you where your money actually goes.
Crawlspace Moisture Protection
Valley-floor farmhouses near the Snoqualmie River corridor see crawlspace humidity that suburban builders never planned for. We wrap trunk lines with vapor-barrier insulation and seal all seams with mastic rated for wet conditions. It’s extra work, but in Duvall’s climate, it’s what keeps a seal intact past the first winter.
HVAC Duct Sealing in Duvall
HVAC Duct Sealing in Duvall means finding every leak in your forced-air system – from crushed flex runs to disconnected boots to gaps where original metal meets newer flexible duct – and closing them with materials that survive our wet winters and rodent pressure. We don’t use foil tape as a permanent fix; it fails in Duvall’s humidity and gets chewed through by field mice moving in from surrounding farmland. Our crews seal with water-based mastic and fiberglass mesh on metal connections, and mechanical clamps with sealed collars on flex-to-boot joints.
Whole-house HVAC duct sealing in Duvall typically costs $450 – $1,200. A single-zone repair on a targeted leak runs $180 – $400. We scope every job with a camera inspection first, so you see what we see before we quote.
Camera Inspection and Leak Mapping
We run a borescope through every accessible trunk and branch before we seal. In Duvall’s older homes, we regularly find previous “repairs” that made things worse: flex duct crammed into too-tight crawlspaces, boots hanging by old tape, sagging runs that pool condensation. The camera footage goes to you, and the quote follows from what we actually found.
Negative-Air Testing After Sealing
After we seal, we pressurize the system and measure leakage with a calibrated fan. Duvall homes with original 1970s metal ductwork often start at 25 – 35% leakage and finish under 10%. You get the before-and-after numbers in writing.
Trusted Brands We Service in Duvall
We stock sealing and insulation products from Abatement Technologies and Guardsman for Duvall jobs, with Rotobrush and Nikro equipment for the cleaning and prep work that often precedes sealing. That local inventory matters because Duvall isn’t a quick run to a major supply house – when we find a crushed flex run or chewed boot on a valley-floor farmhouse, we carry the replacement materials to fix it same visit. No waiting on parts, no second trip, no extra dispatch fee. We also source filtration products from Honeywell and Aprilaire for homeowners who want to upgrade their return air systems while we’re sealing the supply side.
Common Duct Sealing Problems We See in Duvall Homes
- Condensation rot at metal seams. Original 1970s – 80s valley-floor metal trunk lines sweat through damp Snoqualmie Valley winters, so mastic and mesh seals fail at condensation points and need re-sealing far sooner than dry-side homes. We see this on ranchers off Big Rock Road and NE Woodinville-Duvall Road every winter.
- Fall rodent intrusion through flex seams. After harvest, field mice move from surrounding farmland and forest edges into crawlspace duct trunks. They chew through foil tape and flexible duct seams, opening new leaks within a single season after sealing. Every fall sealing job in Duvall includes rodent-exclusion inspection.
- Crushed or kinked flex runs in two-story builds. Duvall’s 1990s – 2010s suburban homes with multiple forced-air zones often have long flexible runs to upstairs bedrooms that sag, kink, or disconnect at the boot. Sealing alone won’t fix a crushed run – the leak returns until the duct is re-routed or supported properly.
- Disconnected boots at hallway and bedroom registers. Decades of vibration, humidity cycling, and patchwork repairs leave boots hanging by old tape or partially detached. We find this constantly in homes where multiple owners have “fixed” the same leak with hardware-store solutions.
Pricing for Duct Sealing in Duvall, WA
Whole-house duct sealing in Duvall runs $450 – $1,200. Single-zone or partial sealing on a targeted problem runs $180 – $400. Duct insulation adds $300 – $800 for partial coverage or $800 – $1,800 for full-house wrap. What moves you within those ranges: crawlspace access (tight digs take longer), duct material (original metal needs more prep than flexible duct), and how many leaks we find (a camera inspection shows you exactly).
We don’t quote per-vent pricing. That’s the bait-and-switch game – a low per-vent teaser that balloons once the technician is inside. We give one flat price per system, agreed in writing before work starts. The price does not move at the door.
Every estimate is free. Call (361) 326-5060 and we’ll schedule a camera inspection at your Duvall home.
We Also Serve Cities Near Duvall
Our crews serve Duvall locally and also handle duct sealing calls from Sammamish, Monroe, Woodinville, and Redmond. Each city gets the same written price guarantee and 365-Day Done Right Promise, though the work itself differs – Sammamish’s dry-side homes don’t face the crawlspace moisture and rodent pressure we plan for in Duvall’s Snoqualmie Valley floor.
Serving Duvall, WA - Our Local Coverage Area
We’re based in the Duvall 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 About Duct Sealing in Duvall
Duvall sits in a wetter microclimate. The Snoqualmie Valley floor gets 38 – 40 inches of rain annually with cool, damp winters that keep crawlspace humidity high year-round. That moisture condenses on metal ductwork and soaks into flex seams, creating mold-friendly conditions. After fall harvest, field mice move from surrounding farmland into those same damp, sheltered crawlspaces. Redmond and Sammamish sit on drier ground with less surrounding agricultural edge habitat, so they see neither the condensation load nor the seasonal rodent pressure. Call (361) 326-5060 if you’re seeing musty airflow or hearing scratching in your vents.
Yes, but only if the flex runs themselves are intact. 1990s – 2010s Duvall builds often have long flexible runs to upstairs bedrooms that sag, kink, or disconnect at the boot. Sealing a crushed run is temporary – the real fix is re-routing or supporting the duct, then sealing the connections. We camera-inspect first and tell you which category your home falls into. A proper seal on good flex lasts years; a seal on damaged flex fails in months. Call (361) 326-5060 for a free inspection.
We start with HEPA filtration and negative-air containment, then run a camera through every trunk and branch. On a 1970s rancher off Big Rock Road, our tech found a crushed flex run to the rear bedroom plus a disconnected boot at the hall register – classic for original metal ductwork that’s been flex-patched over decades. We pulled a mouse nest and acorn cache from the crawlspace trunk, sealed the boot with mastic and mesh, and reconnected the run with new insulated flex. The homeowner immediately noticed the rear bedroom finally heating evenly. Every farmhouse is different, but that combination of original metal, patchwork repairs, and rodent intrusion is typical for Duvall’s valley floor. Call (361) 326-5060 to schedule.
Usually yes, especially for crawlspace or attic runs. Duvall’s humidity means sealed metal trunk lines still sweat and lose energy through thin walls. Insulation wraps the duct after sealing, keeping the conditioned air inside and the condensation outside. We price insulation separately so you can decide after seeing the camera footage. Partial insulation on problem runs runs $300 – $800; full-house wrap is $800 – $1,800. Call (361) 326-5060 and we’ll show you where insulation matters most in your system.
Signs of leaks: uneven heating between rooms, dust blowing from registers right after cleaning, or utility bills that spike without explanation. Signs you need cleaning first: visible mold, rodent debris, or thick dust buildup inside the duct. We often do both – clean first, then seal – because sealing dirty ducts traps contaminants inside. Our camera inspection shows you which problem you have. Call (361) 326-5060 for a free estimate.
Written by Roy Castellanos, Owner at Hollis Air Duct Cleaning, serving Duvall since 2004.