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 Sealing Across Seattle
Duct sealing in Seattle typically runs $800 – $2,400 for a whole-home system, depending on accessibility, duct material, and whether we’re working around original asbestos tape. Most jobs take one day, and we give you a written price before any work starts. Call (361) 326-5060 for a free estimate.
We’ve been crawling through Seattle’s damp basements and tight attics since 2004. Our crews know the difference between a leaky trunk line in a Wallingford Craftsman and a pressure-starved return in a new South Lake Union townhome. Dispatch and scheduling run from our Seattle office, and we carry mastic, mechanical fasteners, and replacement flex sized for the Pacific Northwest’s hybrid heat-pump systems.
Seattle’s wet climate changes the math on duct sealing. With over 150 rainy days a year and crawlspaces that stay humid well into July, a sealed duct that still traps moisture becomes a mold incubator within weeks. That’s why our Duct Sealing team documents every job with before-and-after photos, moisture readings, and written condition reports. We don’t just seal ducts. We seal them in a way that holds up through a Seattle winter.
Why Hollis Air Duct Cleaning Is Seattle’s Preferred Duct Sealing Company
We’ve built our reputation in Seattle on showing up inside the window, pricing in writing, and leaving the site clean. The Garrison Standard requires it, and our technicians are background-checked and uniformed on every job. When you open your door in Ravenna or Ballard, you know who’s walking in.
Our 365-Day Done Right Promise covers every duct sealing job in writing. If the seal fails, the condensation returns, or a taped joint opens up within a year, we come back at no charge. That includes a free second visit. No negotiation, no runaround.
Phones are answered by a live person 24 hours a day, 7 days a week. No voicemail loops, no callback queues, no waiting until Monday to schedule a post-flood inspection.
We know Seattle’s housing stock. Pre-1940 Craftsman bungalows with undersized galvanized trunks. Mid-century ranches in Wedgwood with asbestos tape on every joint. New infill townhomes on Capitol Hill with complex duct runs that fight themselves for pressure. Each type needs a different sealing approach, and we carry the equipment for all of them.
Duct Repair in Seattle
Duct Repair in Seattle often starts with a homeowner noticing uneven heating, a spike in their PSE bill, or a musty smell that gets worse when the system runs. We inspect the full run with a camera, locate the damage, and give you a written repair price before touching anything. Most single-section repairs run $400 – $950; extensive trunk-line work can reach $1,800.
When Repair Beats Replacement
A crushed flex duct in a crawlspace, a separated joint at the plenum, or a small hole chewed by a rodent in Queen Anne’s older homes, these are straightforward fixes. We cut out the damaged section, splice in new material with mechanical fasteners and mastic, and test static pressure before we leave. The repair holds because we match the fix to what the duct actually carries now, not what it carried when it was installed.
Post-Flood Damage Assessment
After water intrusion, some ducts can be dried and sealed. Others are done. We make that call with a borescope camera, moisture meters, and a written condition report. If the insulation is saturated, the inner liner delaminated, or mold has colonized the porous material, we document it and recommend replacement. Our photo sets and moisture readings have been accepted by Seattle-area insurers without reinspection.
Air Duct Sealing in Seattle
Air Duct Sealing in Seattle is as much about moisture control as it is about stopping conditioned air from escaping into your crawlspace. Seattle’s shift to heat pumps and mini-splits means ductwork originally sized for a hot gas furnace now carries cooler, more humid air, creating condensation inside supply runs that is rare in drier cities. This makes duct sealing a moisture-control measure as much as an efficiency upgrade, cold-weather condensation, not dust, is the recurring enemy in Seattle ducts after a storm.
Mastic Sealing for Older Systems
On pre-1940 ductwork with asbestos tape, we don’t just tape over the old joints. We apply UL-181-rated mastic with a brush or spray application, creating a flexible seal that moves with the metal as temperatures swing between 40°F crawlspace air and 70°F conditioned air. Standard foil tape fails within one heating season here from condensation cycling. Mastic doesn’t.
Pressure Balancing on Hybrid Systems
Heat pumps move more air at lower temperatures than gas furnaces. Undersized return ducts create negative pressure that pulls crawlspace humidity into the supply side. We measure static pressure before and after sealing, and if the returns are choking the system, we tell you. Sealing the visible leaks at the air handler while ignoring the return side is a shortcut we don’t take.
Trusted Brands We Service in Seattle
We stock parts and sealing materials from Abatement Technologies, Guardsman, and Rotobrush, the same brands commercial crews use in hospitals and schools. For filtration and humidity control paired with sealed systems, we work with Aprilaire whole-home dehumidifiers and Honeywell media air cleaners. Our Seattle warehouse keeps mastic, mechanical fasteners, and replacement flex in common diameters so we’re not ordering parts while your crawlspace stays open. That means faster turnaround on jobs in Ballard, Wallingford, and down through the Rainier Valley.
Common Duct Sealing Problems We See in Seattle Homes
- Standing water in flex duct after crawlspace flooding. In Seattle’s damp crawlspaces, flexible ductwork often sags and collects standing water from poor drainage, leading to a distinct musty odor that technicians recognize as a sign of hidden mold. Sealing over this traps moisture and accelerates mold growth inside the sealed run. We dry or replace before we seal.
- Failed foil tape on original pre-1940 ductwork. The temperature swing between 40°F crawlspace air and 70°F conditioned air causes condensation cycling that standard foil tape cannot survive. We see this every winter in Craftsman bungalows from Ravenna to Wedgwood. Mastic is the only reliable seal.
- Undersized returns on heat-pump retrofits. Seattle’s decades-long move to heat pumps means many homes have hybrid systems where the original ductwork was sized for a gas furnace. The cooler, more humid air creates condensation and pressure imbalances that pull crawlspace humidity into the supply side. Sealing without measuring static pressure misses the real problem.
- Asbestos tape disturbed during amateur repairs. Pre-1940 homes in Seattle frequently have original asbestos tape on duct joints. Disturbing it without containment and documentation creates a health hazard and a liability issue. We identify it, document it, and seal around it safely.
Pricing for Duct Sealing in Seattle, WA
A typical whole-home duct sealing job in Seattle runs $800 – $2,400. Small homes with accessible crawlspaces and straight trunk lines sit at the lower end. Large homes with multiple zones, complex attic runs, or original asbestos tape requiring careful containment run higher. Single-section repairs are $400 – $950; extensive trunk-line replacement with sealing can reach $1,800 – $2,800.
What moves the price: accessibility (tight crawlspaces take longer), duct material (metal vs. flex vs. fiberboard), the presence of asbestos tape requiring containment, and whether we need to balance pressure on a heat-pump retrofit. We give one flat price per system, agreed in writing before work starts. No per-vent pricing, no add-ons at the door. Call (361) 326-5060 for an exact quote. Estimates are free.
We Also Serve Cities Near Seattle
Our Duct Sealing in Seattle crews also work in Medina, Bellevue, Mercer Island, and Kirkland. Same equipment, same written pricing, same 365-Day Done Right Promise. Dispatch is coordinated from our Seattle office, and we schedule to minimize drive time so we arrive inside the quoted window.
Serving Seattle, WA - Our Local Coverage Area
We’re based in the Seattle 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 Seattle
We inspect first, then decide. If the flex duct holds standing water or the insulation is saturated, we replace that section. If the water missed the ductwork and only the surrounding soil is wet, we dry the area, verify with moisture meters, then seal. Call (361) 326-5060 and we’ll get a technician out to document conditions before mold sets in.
We use a borescope camera to inspect the inner liner, moisture meters to check insulation saturation, and visual assessment for mold colonization. If the inner liner is delaminated, the insulation won’t dry below 15% moisture content, or mold is visible, we recommend replacement and document everything for your insurer. After a storm-driven crawlspace flood in Wallingford, we found a sagging run of flexible duct under a 1920s Craftsman bungalow holding standing water and showing a distinct musty odor. Using a camera inspection and agitation tools under negative pressure, we documented pre-existing asbestos tape on the trunk line before sealing, then sealed the accessible leaks with mastic and replaced the waterlogged flex with a drain-pan pass to the sump. The homeowner’s insurer accepted our before-and-after moisture readings and photo set without a reinspection.
Your ductwork was sized for a gas furnace that pushes 120°F air. Your heat pump pushes 85 – 95°F air at higher volume. The cooler air holds less moisture, and when it meets the humid attic air in Seattle’s climate, condensation forms on the duct surface. Sealing the duct exterior with proper insulation and mastic prevents this. We also check that your returns aren’t pulling humid attic air into the system. Call (361) 326-5060 for a system evaluation.
Yes, but the approach matters. We don’t disturb asbestos tape. We seal around it with mastic, reinforce with mechanical fasteners, and often add external insulation to prevent condensation on the cool metal. The efficiency gain is real, typically 20 – 30% reduction in conditioned air loss. We document the asbestos presence for your records and give you a written condition report.
We provide dated before-and-after photos, moisture meter readings with timestamps, a written scope of work, and a condition report noting any pre-existing asbestos tape or other hazards. Our documentation has been accepted by Seattle-area insurers without reinspection. We know what adjusters need to see to approve the claim the first time.
Written by Roy Castellanos, Owner at Hollis Air Duct Cleaning, serving Seattle since 2004.