Ductwork Replacement Cost Long Island 2026 | Nassau & Suffolk Pricing Guide

Most Long Island homes built between 1955 and 1995 have ductwork that works — it's just leaky, undersized, or under-insulated. Full replacement is rarely the right answer. Watch for these signs that some level of duct work is needed:

• Hot/cold rooms: One bedroom is 8°F warmer than the rest of the house — usually a sizing or leak issue, not equipment
• High summer electric bills despite a newer AC: Conditioned air is leaking into the attic or crawlspace before reaching your rooms
• Dust accumulation: Visible dust in supply registers or behind return grilles means unfiltered air is being pulled in through duct leaks
• Whistling or rumbling sounds: Restricted returns or undersized supplies cause noise complaints
• Visible damage: Crushed flex duct, disconnected joints, asbestos-wrapped pipes, or rusted-through sheet metal
• Upsizing your AC: Going from 2.5 to 4 tons requires duct work to handle the new airflow — otherwise the new system short-cycles and dies young

Here are realistic Nassau and Suffolk County price ranges for the most common ductwork scopes:

Repair & Sealing (Most Common)

• Spot leak sealing (mastic + tape): $450–$1,200
• Reconnect or replace damaged flex runs: $350–$900 per run
• Add or relocate a supply register: $400–$850
• Aeroseal whole-house duct sealing: $1,800–$3,500
• Add insulation to attic ductwork (R-8): $1,200–$2,800

Partial Replacement

• Replace return trunk only: $1,800–$3,800
• Replace one floor of supply runs: $2,500–$5,500
• Replace attic/basement trunk + 3–4 supply runs: $4,500–$7,500

Full Replacement

• Small home (1,200–1,600 sq ft, 1 zone): $4,500–$7,500
• Standard Nassau colonial (1,800–2,400 sq ft): $7,500–$10,500
• Large 2-story (2,500–3,500 sq ft, 2 zones): $10,500–$15,500
• Custom sheet-metal w/ zoning dampers: add $2,500–$5,000

Prices include Manual D sizing, sealing, and R-8 insulation on accessible runs.

Aeroseal is a polymer aerosol that flows through your ductwork and seals leaks from the inside — typically reducing duct leakage from 30%+ down to under 10% in a single 4–6 hour visit. For most Long Island homes, it's the right answer.

Choose Aeroseal when:

• Your ducts are structurally sound but leaky at joints and seams
• You're staying in the home 5+ years and want lower electric bills
• You want minimal disruption (no walls opened, no drywall repair)
• Budget is $1,800–$3,500 instead of $7,500+

Choose full replacement when:

• Ducts are crushed, rusted through, or visibly disconnected in multiple places
• You have asbestos-wrapped ducts (must be abated regardless)
• Ducts are dramatically undersized for a new larger AC or heat pump
• You're doing a whole-home renovation and can open walls anyway

Manual D is the ACCA-published duct design protocol. Done correctly, it sizes every trunk and branch to deliver the airflow each room needs based on the Manual J load calculation. Done incorrectly (or skipped), you get:

• Rooms that never reach setpoint
• Return air starvation that destroys compressors
• Whistling registers, rumbling returns, and constant comfort complaints
• A new AC that runs constantly because the ducts can't move the air

Any contractor proposing $5,000+ in ductwork without a written Manual D is guessing. Insist on it — or call someone who provides one.

Most "you need new ducts" diagnoses are wrong. We start every ductwork project with a static pressure test, a Manual J load calculation, and a written Manual D design so you only pay for the work that actually solves your problem.

Schedule a duct system evaluation or call (516) 259-1191.