Whole-home duct cleaning
Dryer vent cleaning
Camera inspection
Sanitizing & deodorizingWhole-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.
Guardsman Duct Sealing & Repair: The Hempstead Owner’s Guide
Guardsman duct sealing and repair in Hempstead typically runs between $380 and $850 installed, depending on access and how much of the run needs resealing. Roy Castellanos and our crew at Hollis Air Duct Hempstead stock Guardsman-compatible sealing mastic, UL 181-rated tape, and replacement collars on the truck, so most Hempstead jobs are done in a single visit. You usually find out this part has failed when a room that used to heat evenly suddenly runs five degrees colder, or when the utility bill climbs for no obvious reason while the system runs longer than it should.
Most Hempstead homeowners don’t open a wall or crawlspace looking for a failed seam. They notice the symptom first: a bedroom that never quite gets warm in January, a hallway that smells musty, or dust settling on furniture two days after cleaning. The ductwork carries conditioned air through unconditioned spaces, and when a Guardsman seal fails, that air bleeds into the attic or crawlspace instead of the living room. What started as a cracked mastic bead becomes a small energy leak that gets worse every season.
Which Guardsman Models This Applies To
The Guardsman-branded duct sealing products we service in Hempstead fall into three groups: the mastic-sealed sheet metal runs common in 1970s through 1990s construction, foil-faced flex duct connections found in newer additions, and the canvas or fiberglass transition collars at the air handler and supply plenum. Guardsman duct sealing in this market is less about a specific furnace model and more about the duct assembly itself, which is why we match the seal to the duct type, not just the brand sticker.
If you look at the duct near a joint or collar and see a white or gray bead that’s cracked, peeling, or pulling away from the metal, that’s the original mastic that’s given up. Some Hempstead homes built in the 1960s used a rubberized adhesive that dries out and turns brittle; we see it often near Hempstead Lake State Park in the older split-levels along the Southern State corridor. The right replacement for a Guardsman-sealed metal duct is a water-based mastic rated for the full temperature swing of a Long Island attic, not a tube of silicone from the hardware store. Where the duct is foil-faced flex, we use UL 181-listed tape with a mastic overcoat, because tape alone will unpeel at the first summer humidity spike.
On the OEM versus aftermarket question: Guardsman sealing products are primarily commercial-grade mastics and tapes, and there’s no meaningful performance difference between the Guardsman label and a quality water-based equivalent for residential use. What matters is the rating, not the branding. We carry what meets the standard and we’ll show you the label before it goes on.
Styles & brands we work with
Signs Your Guardsman Duct Sealing & Repair Is Failing
- Uneven room temperatures across Hempstead’s split-levels. When a seal fails in one branch run, that room loses conditioned air before it arrives. The rest of the house runs normal while one room stays cold, and the thermostat never catches up because it’s reading the warmer part of the house.
- Dust on surfaces within a day or two of cleaning. A failed return-side seal pulls air from the attic or wall cavity instead of the return grille. That unfiltered air carries insulation fibers and settled dust straight into the living space.
- Musty smell that worsens when the blower kicks on. When a seal fails on the return side near a crawlspace or attic with any moisture, the system draws that damp air across the coil and distributes it through every register. You smell it in every room, not just one.
- Higher heating bills with no change in thermostat habits. A 3% to 15% loss through failing duct seals is typical in older Hempstead homes, and it shows up in January and February when the system runs longest. One open seam at the supply plenum can lose enough air to matter.
- Visible gaps, cracks, or torn foil at the joints. If you can see daylight between the duct collar and the plenum, or if the foil tape is peeling at the seams, the seal is already gone. The fix is removing the failed material and resealing, not taping over it.
Replacement Cost & What’s Included
In Hempstead, resealing a failed Guardsman duct seal runs $380 to $850 installed. A single accessible joint or collar repair on a basement-accessible run lands at the low end; resealing the full supply plenum or repairing return-side leaks in a tight attic pushes toward the top. The price includes removal of the failed mastic or tape, surface preparation, new sealing material applied per the duct type, and an inspection of adjacent joints so we’re not sealing one seam while the next one is already cracked.
We write the price before we start, and it does not move once the work begins. You’ll know the cost for the exact repair the system needs, not a teaser number that becomes something else once the technician is in the crawlspace. Every repair we make in Hempstead is covered by our 365-Day Done Right Promise: if a seal we apply fails within a year, we return and make it right at no charge, including a free second visit.
See the difference
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After
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After
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AfterDIY or Call Us?
What you can safely do as a Hempstead homeowner is look for obvious signs of failure: cracked mastic, peeled tape, visible gaps at the supply or return collars, and rooms that run consistently colder than the rest of the house. That inspection costs nothing and helps you describe exactly what you’re seeing when you call. Duct sealing itself is not a high-voltage or high-tension job, but it is a job where the access matters more than the material. Most Hempstead ductwork runs through attics with low clearance, tight chases, or crawlspaces where a bad seal is hidden behind a finished wall.
Where DIY goes wrong is almost always surface preparation. Mastic over a dusty, greasy joint pulls away within a season, and the homeowner is back to square one with material cost wasted. The other failure point is reach: a joint you can see from the attic hatch may extend six feet past where you can safely work it. If you’ve already spotted the failed seal and you want it fixed once, call us at (516) 559-4917 and we’ll write the price before we touch anything.
FAQs
A properly applied duct seal in Hempstead’s climate should last 15 to 25 years before the mastic dries out or cracks from attic temperature swings. If a seal applied within the last two years is already failing, the original prep work is usually the culprit. Call (516) 559-4917 and we’ll inspect the seal we’re replacing as part of the job.
A failed duct seal can almost always be repaired by removing the failed material and applying a fresh seal to a properly cleaned surface. Full duct replacement is only needed when the metal or flex duct itself has rusted through or torn. We’ll give you a written price for the repair as it stands without adding replacement work you don’t need.
A typical single-joint or collar reseal takes 1 to 2 hours, including cleanup and a quick check of adjacent seams. Full supply plenum resealing in a Hempstead attic can take half a day depending on access. We schedule a window and we arrive inside it; the job is done by the book and the site is left clean when we leave.
Yes. Our trucks carry water-based mastic, UL 181-rated tape, replacement collars, and the hand tools needed for the job. We also stock parts for Lennox, Trane, and Carrier systems, so if the seal failure turns out to be part of a bigger issue at the supply plenum, we can address it the same day without a return trip.
Cheaper quotes usually cover less actual work: a thin bead of mastic over the existing failed material, or tape over a cracked joint without any surface preparation. Those fixes fail within a season, and the low price was the point. A real reseal removes the failed material first, and the price should be written down before the work starts. Ours is, every time.
Get a Written Price for Your Guardsman Duct Repair in Hempstead
If you’ve found a failed seal, a cold room that won’t behave, or dust that comes back too fast, call us at (516) 559-4917 for a free estimate. We’ll look at the duct, write down the price, and tell you what’s actually wrong before we touch a thing. Clean ducts, straight answers, that’s the whole job.
Written by Roy Castellanos, Owner, Hollis Air Duct Hempstead at Hollis Air Duct Hempstead, serving Hempstead and nearby areas.