Duct Repair & Sealing Cost - Tested First, Written Price Second

How Much Does Duct Repair & Sealing Cost in Hempstead?

Duct repair and sealing in Hempstead, NY typically costs between $350 and $1,300 for most homes, with the average job landing around $700. Smaller repairs like patching a single disconnected joint run $150 to $300, while full-system sealing with mastic and Aeroseal-type application on a 2,000-square-foot house can reach $1,800 to $2,500. Labor rates for licensed duct technicians in Nassau County run $75 to $125 per hour, and most repair-and-seal jobs take between four and eight hours to complete properly.

These numbers come from jobs our crews have priced across Hempstead Village, Uniondale, West Hempstead, Franklin Square, and the surrounding Nassau County market through 2025, adjusted for 2026 material costs. The range is wide because duct systems differ enormously from house to house. A 1950s colonial with accessible basement ducts costs far less to seal than a 1980s split-level where half the ductwork runs through finished ceilings.

Duct Repair & Sealing Cost Breakdown (2026)

Here’s what our written estimates look like in Hempstead for 2026, broken down by job type. These are the numbers we put in writing before any work begins.

Job Type	Typical Range (Hempstead, NY)	What It Includes
Single duct joint repair	$150 – $300	One disconnected or leaking joint at an accessible location; sheet metal screws, foil tape, or mastic as needed; 45-90 minutes of labor.
Small section replacement (3-10 linear feet)	$250 – $550	Cutting out and replacing a crushed or rusted duct run; includes materials, hangers, and sealing at both connection points.
Full duct sealing (accessible ducts)	$600 – $1,200	Mastic-sealing all accessible joints and seams in a basement or crawlspace system; typically 2,000-3,000 sq ft home; includes before/after inspection.
Full duct sealing (partially accessible)	$1,100 – $1,800	Sealing accessible runs plus camera-assisted inspection and repair of runs behind finished walls where reachable; often requires access holes that we patch and finish.
Aeroseal-type aerosol sealing	$1,500 – $2,500	Whole-system pressurized sealing from the inside; covers leaks in the duct walls themselves, not just joints; single-day job; includes pressure testing before and after.
Return air plenum repair	$400 – $900	Repairing or rebuilding the main return air box where ductwork meets the furnace; includes mastic sealing and sometimes new sheet metal fabrication.
Insulation wrap (add-on)	$4 – $7 per linear foot	Fiberglass or closed-cell foam wrap for ducts running through unconditioned attics or crawlspaces; typical add-on of $200-$450 for a standard home.

What moves a job toward the top or bottom of these ranges? In Hempstead specifically, we see three consistent drivers. First, access. Homes in the Village of Hempstead and older sections of Uniondale often have low crawlspaces and tight basement clearance, which means more labor hours. Second, duct material and age. Galvanized steel from the 1960s and 1970s takes mastic well and seals permanently; older fiberboard ductboard from the 1950s can be brittle, and sometimes needs more replacement than repair, pushing cost up. Third, system configuration. Split-level homes common in West Hempstead and Franklin Square have duct runs that cross multiple floor planes, which means more joints, more seams, and more time.

One more honest note: if your ducts contain asbestos-wrapped insulation, which shows up occasionally in pre-1975 Hempstead homes, the repair cost is not in the table above. Asbestos abatement is a licensed, regulated process handled by specialized contractors, and Nassau County requires specific permits. If we see it, we stop and tell you exactly what’s needed before any work proceeds. We don’t touch it, and neither should an untrained crew.

What Affects Duct Repair & Sealing Pricing in Hempstead

• Access to the ductwork. A full basement with exposed joists is the cheapest scenario. A finished basement ceiling, a low crawlspace, or ducts running through a finished attic wall changes labor time significantly. In Hempstead’s older colonial and cap-cod stock, we regularly see return ducts buried behind finished drywall, which means cutting access holes, doing the repair, and patching cleanly afterward.
• Number of leaks and their location. One loose supply boot at the floor register is a 30-minute fix. Thirty leaking joints spread across a 40-foot trunk line is a full-day job. We use a combination of visual inspection, smoke testing, and in some cases a duct blaster pressure test to locate every leak before quoting, so the price on paper matches the actual work.
• Duct material and condition. Solid galvanized steel in good shape seals beautifully with mastic at the seams. Rusted steel, crushed flex duct, or degraded ductboard often requires section replacement, which adds material cost. Hempstead’s coastal humidity, especially in homes near Hempstead Lake State Park and the South Shore creeks, accelerates rust on exposed basement ducts.
• System size and layout. A 1,200-square-foot ranch has maybe 150 linear feet of ductwork. A 3,500-square-foot center-hall colonial can have 400 feet or more, with branches to multiple floors. More duct means more joints, more boots, more sealing time.
• Whether insulation is needed. Ducts running through unheated attics or vented crawlspaces lose energy even after sealing. Adding wrap insulation is a per-foot cost that can add $200 to $500 to a typical job. It’s optional, but in a Hempstead winter with January lows in the 20s, uninsulated attic ducts bleed heat fast. We give you the itemized option and let you decide with the numbers in front of you.
• Permit requirements. Most duct repair and sealing work in Hempstead does not require a building permit, assuming it’s repair in kind rather than new installation. But if a duct run is being substantially reconfigured, the Town of Hempstead Building Department may require a permit, and that adds $100 to $300 in fees plus a few days of wait time. We’ll tell you upfront if your job triggers that.

How to Save on Duct Repair & Sealing

You can reduce the final number without cutting corners. Here’s what actually works in Hempstead.

Get a written, itemized price before work starts. This sounds obvious, but a huge share of the jobs we repair after other companies did the work have one thing in common: the original quote was verbal, vague, or “per leak” with no leak count. A written price with line items means you’re comparing apples to apples, and it gives you a record if the work doesn’t hold up. At Hollis Air Duct Hempstead, the price is written down before our technician touches a single joint, and it doesn’t move at the door.

Bundle repair with a duct cleaning. If your ducts have never been cleaned or it’s been more than five years, the inside of the ductwork often has a layer of dust, pet hair, and debris that prevents mastic from bonding cleanly. Doing the cleaning and the sealing in the same visit saves a second mobilization charge, which typically runs $75 to $150 in Nassau County. Our crews use negative-air machines from Nikro and rotary brush systems from Rotobrush to clean first, then seal. One trip, one written price.

Seal what’s accessible before tackling what isn’t. If half your ducts are in an open basement and half are buried in walls, sealing the open half can recover 60-70% of the loss at a fraction of the cost of an Aeroseal-type whole-system job. We’ll tell you honestly whether that partial job makes sense for your home or whether the buried runs are leaking badly enough that the full job pays for itself.

Check whether your utility offers a rebate. As of 2026, New York State continues to fund duct sealing through some home-efficiency programs, and PSEG Long Island has periodically offered incentives for duct sealing when paired with an energy assessment. Eligibility shifts year to year, and we recommend you confirm current program status directly with PSEG or NYSERDA before scheduling. We don’t administer rebates, but we’ll give you the invoice documentation you need to apply.

Don’t wait until the middle of summer or winter. Duct techs in Hempstead are busiest when the weather is worst. Booking in spring or fall gives you more scheduling flexibility, and some companies, including ours, have more room to hold pricing during those shoulder seasons. If your system is inefficient but still running, a planned repair beats an emergency call.

For a free, written estimate on duct repair or sealing in Hempstead, call (516) 559-4917. We answer the phone with a live person, 24 hours a day, and we’ll schedule you a specific arrival window, not a four-hour “sometime.”

What Does Duct Repair and Sealing Actually Include?

It’s worth knowing exactly what you’re paying for when the invoice says “duct repair and sealing.” Here’s the plain-English version, because the trade uses words that get thrown around without explanation.

Duct sealing mastic is a brush-on or trowel-on paste that hardens into a flexible, airtight seal at duct joints and seams. It’s not duct tape. Duct tape, ironically, fails on ducts within a few years in Hempstead’s humidity cycles; it dries out, peels off, and leaves the same leak you paid to fix. Mastic is the standard for a reason: it doesn’t shrink, it doesn’t separate with vibration, and it lasts the life of the duct material when applied correctly.

Negative-air duct cleaning means we connect a large vacuum unit that creates negative pressure inside your duct system, so that debris gets pulled toward the collection point rather than blown into your living space. When we do a repair-and-seal visit, we use this same setup to draw dust out before sealing, so the mastic bonds to metal, not to the layer of film that accumulates inside duct walls over years.

Aeroseal-type sealing is a different method: a sealing machine pressurizes the duct system and injects an aerosolized sealant that deposits at the leak points themselves, sealing from the inside. It’s effective for ductwork you can’t reach, and it carries the highest price tag in our table for that reason. It’s not always necessary. If we can reach your leaks with a brush, mastic is cheaper and every bit as permanent. We’ll recommend the right tool, not the most expensive one.

Supply and return sides. Your system has two networks: supply ducts push conditioned air from the furnace or air handler into rooms; return ducts pull air back to be reheated or recooled. Both leak, but leaks in the return side pull in air from basements, crawlspaces, and wall cavities, which means dust, humidity, and in some Hempstead homes, trace amounts of gasoline or paint fumes from attached garages. A proper sealing job addresses both sides, and any written quote should say so explicitly.

Why Duct Leaks Matter More in Hempstead Than Homeowners Expect

Hempstead’s climate works against leaky ducts in two directions. In winter, when temperatures average in the mid-30s with regular dips into the teens, supply ducts running through unheated basements and attics lose conditioned air before it reaches the register. You pay to heat air that ends up in the crawlspace. In summer, when Long Island humidity sits above 70% for weeks at a time, return ducts in basements pull damp, musty air into the system, making your AC work harder to remove moisture it never should have pulled in.

We also see a Hempstead-specific issue with homes near the Southern State Parkway and Hempstead Turnpike corridors: fine particulate from traffic and construction makes its way into unsealed duct joints in basements with outside access. The return side is negative-pressure; it’s actively sucking air from wherever it can get it, including gaps around foundation penetrations. Sealing the ducts doesn’t fix the foundation, but it stops the duct system from pulling that outside air into your living areas.

Roy Castellanos, who heads our Hempstead operation, puts it this way: the duct system is the lungs of the house. If the lungs have holes, the house is breathing air from wherever those holes are, not from the rooms you’re trying to keep comfortable.

Repair or Replace: Which Makes Sense?

The most common question we get on every estimate visit is whether sealing makes sense or whether replacement is the better call. Here’s the honest answer we give in Hempstead homes every week.

If your ductwork is galvanized steel, less than 40 years old, and has not been flattened, rusted through, or badly corroded, sealing is almost always the right move. Steel ducts have no lifespan issue; the material itself doesn’t wear out, and mastic at the seams restores a 30-year-old system to near-new efficiency. Replacing good steel because it leaks is like replacing a roof because one shingle shifted.

Replacement makes sense when: the ducts are made of old fiberboard ductboard that’s crumbling or saturated with moisture; the runs are rusted through, not just surface-rusted; sections are collapsed or so dented that airflow is restricted; or the original installation was so poorly sized or routed that no amount of sealing fixes the imbalance. In those cases, we’ll tell you directly and give you a written replacement price alongside the sealing price, so you’re making the decision with both numbers in hand.

Full duct replacement in Hempstead runs $3,500 to $8,000 for a typical 2,000 to 2,500-square-foot home, assuming accessible runs and standard galvanized installation. That number is for context, not an upsell. Most homes we see need sealing and modest repair, not replacement.

What Does the 365-Day Done Right Promise Cover?

Every duct repair and sealing job from Hollis Air Duct Hempstead includes the 365-Day Done Right Promise, and we put it in writing before the job starts. Here’s exactly what it says.

If any duct repair or sealing work we perform fails within one year – a joint opens back up, a seal separates, a section we replaced comes loose – we return and make it right at no charge. That includes a free second visit. No pro-rating. No “that’s wear and tear.” No dispatch fee. You call, we come back, we fix it.

This is part of The Garrison Standard, the operating code our parent company applies to every independently owned Hollis location. The standard covers what happens on the job too: the technician arrives inside the quoted window, the price is in writing before any work begins, the work is done by the book, and the site is left clean. If any of those fail, the 365-Day Done Right Promise is our correction mechanism. We don’t ask you to take our word on trust; we put the guarantee in writing and sign it.

Roy Castellanos has held our Hempstead crew to this standard since the location opened under the Garrison Partners family, which founded the Hollis brand in 2004. In a market like Nassau County where homeowners have dealt with no-shows and door-step price increases, a written guarantee with a named owner behind it is the difference between a handshake and a contract.

How to Spot Duct Leaks Before They Get Expensive

You don’t need specialized equipment to know something’s wrong. Here are the signs we tell Hempstead homeowners to watch for, because catching leaks early keeps a $300 repair from becoming a $1,500 sealing job or a full replacement.

Rooms that never reach the thermostat setting. If your living room is comfortable but the back bedroom is always five degrees off, and the registers in that room are fully open, you likely have leakage along the supply run to that room. The conditioned air is being lost in the basement or wall cavity before it hits the register.

Dust that returns within days of cleaning. Return-side leaks pull air from unconditioned spaces. Dusty basement air, crawlspace air, even wall-cavity air with insulation fibers gets pulled into the return stream and distributed through the house. If your furniture develops a visible dust layer days after you wipe it down, watch the return ducts.

Higher-than-expected summer and winter bills. The Department of Energy has estimated for years that typical duct systems lose 20 to 30 percent of conditioned air to leaks. If your Hempstead home’s heating and cooling costs have crept up while the thermostat habits haven’t changed, duct leakage is one of the first things we check.

Musty or unusual smells in specific rooms. A return duct pulling from a damp crawlspace or a musty basement distributes that odor selectively. If one room smells off and the others don’t, trace the duct path before you buy a dehumidifier.

None of these signs require you to climb into the crawlspace or open a wall. If you’re seeing two or more, call (516) 559-4917 and we’ll send a technician to inspect and give you a written price for whatever, if anything, the system actually needs.

FAQs – Duct Repair & Sealing Cost

How much does it cost to seal ductwork in Hempstead?

Sealing accessible ductwork in an average Hempstead home costs $600 to $1,200. Whole-system sealing that includes hard-to-reach sections, or an Aeroseal-type job that seals from the inside, runs $1,500 to $2,500. For a written price on your specific system, call (516) 559-4917 for a free estimate.

Is it cheaper to repair or replace ductwork?

Repair is dramatically cheaper in most cases. Sealing and minor repair costs $350 to $1,300, while full duct replacement in Hempstead runs $3,500 to $8,000. Replacement is only the right call when ducts are rusted through, collapsed, or made of deteriorated ductboard. We’ll give you both numbers in writing if your situation warrants it.

How long does duct sealing take?

Most repair-and-sealing jobs take four to eight hours, including job setup, cleaning prep, sealing, and cleanup. An Aeroseal-type whole-system job can be done in a single day. We arrive inside a quoted window and leave the site clean when the job is done.

Can you seal ducts without tearing out walls?

Yes. For ducts inside finished walls or ceilings, Aeroseal-type sealing reaches leaks from the inside through the duct system itself, with no wall demolition. For accessible basement and attic runs, mastic sealing requires no demolition at all. If access holes are needed, we cut them, do the work, and patch them cleanly.

How much does emergency duct repair cost in Hempstead?

Emergency repair, meaning a same-day or next-day call for a detached or crushed duct that’s left part of your home unheated or un-cooled, typically runs $200 to $500, depending on what’s wrong. Our phones are answered by a live person 24/7 at (516) 559-4917, and we’ll give you the price in writing before anyone starts working.

Does homeowners insurance cover duct repair?

Homeowners insurance typically covers duct damage only when it results from a covered peril, like a fire, a burst pipe, or a fallen tree. Normal deterioration, rust, or gradual joint separation, which is most of what we see in Hempstead, is considered maintenance and is not covered. If your damage came from a covered event, we’ll give you the invoice and photo documentation your insurer needs.

Key Takeaways

• Duct repair and sealing in Hempstead, NY costs $350 to $1,300 for most jobs, with the average around $700.
• Labor rates for licensed duct techs in Nassau County run $75 to $125 per hour.
• Full-system Aeroseal-type sealing runs $1,500 to $2,500; full duct replacement runs $3,500 to $8,000.
• Get a written price before work starts. If a company won’t put the number on paper, call someone who will.
• Hollis Air Duct Hempstead covers every repair and sealing job with the 365-Day Done Right Promise: if it fails within a year, we come back at no charge, including a free second visit.

Get a Written Duct Repair & Sealing Estimate in Hempstead

If your ducts are leaking and you’re ready for a number, not a sales pitch, call Roy and our team at Hollis Air Duct Hempstead. We’ve been part of the Hempstead and Nassau County market since 2004 under the Garrison Partners family, and we run every job by The Garrison Standard: arrive inside the quoted window, put the price in writing before we touch anything, do the work by the book, and leave the site clean.

Our technicians are background-checked and uniformed. Our equipment is professional-grade: Rotobrush rotary brush systems, Nikro negative-air machines, and filtration products from Honeywell, Aprilaire, Abatement Technologies, and Guardsman. Our phones are answered by a live person 24 hours a day, 7 days a week, at (516) 559-4917.

Every duct repair and sealing job we do includes a written price before the work starts and the 365-Day Done Right Promise in writing. If the work fails within a year, we come back and make it right, at no charge. That’s not a marketing line. That’s the contract.

Call (516) 559-4917 for a free estimate, or learn more about our Duct Repair & Sealing in Hempstead service. New to Hollis? Start at our home page to see everything we do. If you’re in Uniondale, West Hempstead, Franklin Square, Baldwin, Rockville Centre, Garden City, East Meadow, or anywhere else in Nassau County, same service, same standard, same written guarantee.

Pricing reflects the Hempstead market as of 2026. Hollis Air Duct Hempstead offers free estimates – call (516) 559-4917.

Written by Roy Castellanos, Owner at Hollis Air Duct Hempstead, serving Hempstead and Nassau County since 2004.