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 San Marcos
Duct sealing in San Marcos typically runs $350 – $850 for a whole-home system, and most jobs finish in a single visit. We’re Hollis Air Duct Cleaning, part of the Garrison Partners family, and our crews work San Marcos from the original core near Mission Road out to the newer tracts along the SR-78 corridor and the canyon edges near San Elijo. Scheduling runs through our Austin office, but the technicians who arrive at your door live and work this corridor – they know the builder-standard layouts from the 1980s and 1990s builds, the flexible duct runs common in Rancho Santa Fe and Discovery Hills, and what the dry inland climate does to tape and mastic over time. Call us at (361) 326-5060 for a free estimate.
Why Hollis Air Duct Cleaning Is San Marcos’s Preferred Duct Sealing Company
We’ve been in business since 2004, and our reputation in San Marcos is built on showing up inside the window and pricing in writing before we touch anything. Our technicians are background-checked, uniformed, and trained on The Garrison Standard – arrive on time, price before work, finish by the book, leave the site clean. The 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.
Phones are answered by a live person 24 hours a day, 7 days a week. No voicemail loops, no callback queues. When you call (361) 326-5060, you talk to a human who can schedule your San Marcos appointment and confirm your written estimate.
Duct Insulation in San Marcos
Duct Insulation in San Marcos addresses a problem the hot inland summers make worse: attic temperatures in tract homes off Twin Oaks Valley Road routinely climb past 130°F, and uninsulated or poorly insulated flex duct bleeds that heat straight into your cooled air before it reaches the register. We wrap or replace insulation on supply runs, paying special attention to the short, tightly routed flex lines common in 1990s and 2000s San Marcos builds where there’s no slack to reroute.
Most San Marcos homeowners need duct insulation work when rooms at the far end of the system blow warm while others are ice-cold, or when energy bills spike in July and August despite the thermostat never moving. A typical duct insulation job in San Marcos runs $400 – $900 depending on linear footage and attic accessibility.
Attic Heat Gain in Tract Homes
The shallow attics in San Marcos master-planned communities trap heat against the ductwork. We use insulation rated for our climate zone, sealed at seams with mastic, not tape that dries and peels.
Insulation After Sealing
We insulate after we seal. A leaky duct wrapped in new insulation just leaks into the insulation. Our crew tests with a pressure pan before and after so you see the difference.
HVAC Duct Sealing in San Marcos
HVAC Duct Sealing in San Marcos fixes the gaps that open where flex duct meets the plenum, where boots connect to drywall, and at joints the builder’s crew taped and forgot. In the 1980s-through-2000s housing stock that dominates this city, those connections were often pinch-clamped and wrapped with foil tape – not mastic-sealed – and the dry heat plus Santa Ana wind cycles crack the adhesive within the first few years.
San Marcos homeowners call us for HVAC duct sealing when they notice uneven temperatures room to room, dust blowing from registers even after filter changes, or that chemical “new house” smell that never quite goes away. A whole-home HVAC duct sealing in San Marcos typically costs $350 – $850, with larger two-story tracts or homes with multiple zones running toward the higher end.
Mastic Sealing Versus Tape
We apply duct sealing mastic, a water-based compound that remains flexible and bonds to metal, flex, and drywall. Tape fails. Mastic doesn’t. We brush it on every joint, boot, and plenum connection.
Pressure Testing After Sealing
Our crew runs a duct blaster or pressure pan test to measure leakage before and after. You get the numbers. If the system doesn’t meet our standard, we keep working until it does.
Trusted Brands We Service in San Marcos
We carry professional-grade equipment from Rotobrush, Nikro, and Abatement Technologies – the same rotary brush systems and negative-air machines commercial crews use. For filtration and sealing products, we stock Honeywell, Aprilaire, and Guardsman components, so San Marcos homeowners don’t wait on parts shipped from out of state. Whether your system is builder-standard from a 1995 Discovery Hills tract or a newer variable-speed install in a San Elijo Hills townhome, we have the fittings and the know-how to seal it right.
Common Duct Sealing Problems We See in San Marcos Homes
- Builder-grade flex duct gaps at the plenum. In Rancho Santa Fe, Discovery Hills, and similar 1980s – 2000s tracts, the flex duct was clamped to the plenum with a zip tie and wrapped in foil tape. The tape dries, the gap opens, and hot attic air pulls straight into your supply. We see this in homes five years old or fifty.
- Construction debris circulating in new builds. Drywall dust, sawdust, and fiberglass fragments stay loose in San Marcos ducts because the dry inland air never lets them settle. Every blower cycle pushes them through the registers. Sealing the returns and supply boots stops the recirculation path.
- Wildfire ash intrusion through unsealed returns. When Santa Ana winds push fire smoke up the SR-78 corridor, canyon-edge homes near San Elijo and ridgeline properties suck fine soot through gaps in return-air joints. The ash stains the duct long before the filter looks dirty. Sealing those joints is fire-hardening, not just efficiency.
- Pinched flex runs in tight attic spaces. San Marcos tract builders routed short flex lines through shallow attics with sharp bends. The duct kinks, airflow drops, and the homeowner cranks the thermostat. We seal and sometimes reroute for proper airflow.
Pricing for Duct Sealing in San Marcos, TX
A typical duct sealing job in San Marcos runs $350 – $850 for a whole-home system. Single-story homes in the original core with straightforward attic access usually fall in the $350 – $550 range. Two-story tracts in Rancho Santa Fe or San Elijo Hills, or homes with multiple HVAC zones and complex attic runs, trend toward $650 – $850. What moves the price: linear footage of ductwork, number of plenum and boot connections, whether we need to remove old tape and debris first, and if insulation replacement is part of the same visit.
We give one flat price per system, agreed in writing before any work starts. No per-vent pricing, no add-ons at the door. Every estimate is free. Call (361) 326-5060 and we’ll schedule a look.
We Also Serve Cities Near San Marcos
Our crews work the full North County corridor. If you’re in San Marcos or nearby Kyle, New Braunfels, Buda, or Canyon Lake, the same Garrison Standard applies: written price, background-checked uniformed technician, 365-Day Done Right Promise. Duct Sealing appointments are scheduled through our Austin office with local crews dispatched to your area.
Serving San Marcos, TX - Our Local Coverage Area
We’re based in the San Marcos 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 San Marcos
Because builders rarely commission a NADCA-standard clean before closing, and construction debris stays loose in San Marcos’ dry air. Drywall dust, sawdust, and insulation fragments recirculate with the first summer of year-round HVAC use. A family in the Rancho Santa Fe tract off the SR-78 corridor called us three weeks after closing – every time the air handler kicked on, the whole house smelled like drywall dust. Our camera inspection found construction debris and drywall chunks in the return drop and coating the flexible runs to the upstairs registers. We pulled negative pressure on the system, ran agitation tools through every branch, HEPA-filtered the exhaust, and finished with duct sealing at the plenum and boot connections – the first thing the builder’s crew should have done before the keys changed hands. Call (361) 326-5060 for a free estimate.
Tract homes use shorter, tightly routed flex duct with pinch-clamp connections, while older core homes near Mission Road often have metal duct with screwed joints and more attic space to work. The tract flex requires mastic sealing at the plenum and boots – tape fails quickly in our heat – and the tight runs mean we sometimes reroute for proper airflow. Older metal duct may need seam sealing and register boot replacement instead. Call (361) 326-5060 and we’ll assess what your specific system needs.
Yes. When Santa Ana winds meet a wildfire in the hills east of the 78, the first call wave comes from canyon-adjacent neighborhoods near San Elijo and the ridgelines. Ash and fine soot enter through unsealed return-air joints, staining ducts long before filters clog. Sealing those joints with mastic creates a barrier that keeps particulate out of the system. It’s fire-hardening your HVAC, not just efficiency work. Call (361) 326-5060 to schedule an inspection.
We seal both. San Marcos has significant apartment and townhome stock, especially near the university and in newer master-planned communities. Multi-unit jobs require coordination with property management and sometimes access to common mechanical areas, but the sealing process is the same: mastic at joints, pressure test, verify. We price per system, in writing, before starting. Call (361) 326-5060 to discuss your building.
We inspect with a camera, seal every joint and boot with mastic, then pressure-test the system and show you the before-and-after leakage numbers. If the reduction doesn’t meet our standard, we keep working. You also get before-and-after photos of your own ducts. The 365-Day Done Right Promise covers the work: if a seal fails within a year, we return at no charge. Call (361) 326-5060 to book your free estimate.
Written by Roy Castellanos, Owner at Hollis Air Duct Cleaning, serving San Marcos and the surrounding communities.