Ductwork Replacement Cost in Apex

Leaky, crushed or poorly designed ducts waste energy and make rooms uncomfortable. In Apex, many ducts run through vented crawl spaces or hot attics, where leaks pull in humid or hot air.

This guide covers costs and options.

Published costs

Published 2026 estimates put duct replacement at $452–$2,181, averaging about $1,250, or $10–$25 per linear foot. For a 2,000-square-foot home with about 250 feet of ductwork, published estimates run $2,000–$4,500. New ductwork installation averages about $4,000, typically $2,000–$7,500.

Signs of duct problems

Rooms that never reach set temperature, high humidity, dusty air, whistling registers, visible disconnected or crushed ducts, and high bills.

Sealing vs. replacement

Sealing joints with mastic and insulating ducts can fix many issues. Replacement makes sense for damaged, undersized or poorly routed ducts.

Crawl spaces and attics

Ducts in crawl spaces can sweat in summer; closed crawl spaces under the NC code include duct sealing requirements. Ducting supply air into a closed crawl space requires an H-3 license per OSFM.

Design matters

New ducts should be designed for airflow, using Manual D style sizing methods, with returns sized to the system. Undersized returns are a common cause of noise and poor performance.

Coordinating with equipment replacement

If your system is also near the end of its life, replacing ducts and equipment together lets the contractor design ducts for the new system's airflow and avoid paying for access twice. Ducts sized for an old system can limit a new, efficient unit.

What a duct evaluation should include

A thorough evaluation measures airflow at registers, checks static pressure, inspects ducts for disconnections, crushed sections and missing insulation, and may include a duct leakage test. In crawl spaces, the contractor should look for ducts lying on the ground, sagging flex duct and condensation on duct surfaces. In attics, look for kinked flex runs and gaps at boots. Ask for photos and a written summary of what was found and how each problem will be fixed. Compare proposals on scope: full replacement, partial replacement and sealing are very different jobs with very different prices.

Working with a referred HVAC contractor

Before signing, confirm the contractor's North Carolina heating and cooling license and insurance, ask who pulls the Town permit, and get the equipment model numbers, warranty registration and expected install date in writing. Ask what happens if ductwork problems are found during installation and how changes will be priced. Keep permit and inspection records with your home files.

Testing ducts

Duct leakage tests measure how much air escapes. Ask for before-and-after results when sealing or replacing ducts.

Insulation

Ducts in attics and crawl spaces should be insulated to reduce condensation and energy loss.

Permits

Duct alterations and extensions are mechanical permit work in Apex.

Common duct problems in Apex homes

Flexible duct in crawl spaces and attics can sag, kink or separate at joints over time, especially where it was hung without enough support. Rodents and pests can tear insulation. Metal trunk lines can corrode in wet crawl spaces. Each of these problems reduces airflow to some rooms, raises energy use and can pull humid or dusty air into the system through return leaks. Rooms that are always too hot or too cold, high energy bills and dust around registers are common clues.

A technician can inspect visible ducts, measure static pressure at the air handler and, with the right equipment, test total duct leakage. Those measurements help decide whether sealing and repairs are enough or whether a section, or the whole system, should be replaced.

Sizing and layout

Replacement is a chance to correct original design problems. A room-by-room load calculation and a duct design based on it tell the installer how much air each room needs and what size each run should be. Ducts that are too small make a system noisy and strain the blower; ducts that are too large can lower air velocity so rooms near the end of the run get little air. Adding returns to closed bedrooms often improves comfort.

Coordinating with crawl space work

If the crawl space is wet, fix drainage and moisture before installing new ducts there. New ducts in a damp space will sweat and deteriorate. If you plan to convert to a closed crawl space, coordinate the duct layout and any supply-air drying with the HVAC contractor, because supply-air drying must be installed by a licensed heating contractor and the conversion is permitted work.

Comparing duct bids

Ask each bidder whether the price covers full replacement or selected runs, the duct materials and insulation values, how joints will be sealed, whether registers and boots are replaced, and whether leakage testing is included. Ask how old ducts will be removed and disposed of. Confirm the mechanical permit is included. Comparing before-and-after leakage numbers is the clearest way to see what the new ductwork achieved and to hold the contractor to the scope you paid for.

Published HVAC cost estimates

Sources: Angi: Mini-split installation cost (2026); Angi: Ductless HVAC system cost (2026); Angi: Duct replacement cost (2026); Angi: Furnace cost (2026); Angi: HVAC maintenance cost (2026); Angi: HVAC replacement cost (2026). Figures are published national or regional estimates compiled by those sites, labeled as estimates; they are not quotes and not prices from any provider on this site. National published estimates; Apex homes with ducts in crawl spaces or attics, multi-story layouts or older equipment can price higher.

Local rules and code references

• Town of Apex, When do you need a permit?: lists replacing and reconnecting furnaces and adding to or modifying the heating and air conditioning system as work that requires a permit regardless of cost.
• Town of Apex, Obtaining a Building Permit: residential single-trade mechanical permits must be submitted through ePermits by a licensed contractor.
• N.C. Gen. Stat. §160D-1110: subsection (a)(3) requires permits for the installation, extension, alteration or general repair of any heating or cooling equipment system; the $40,000 exemption in subsection (c) does not apply to the addition, replacement or design change of heating or air-conditioning equipment (c)(3).
• NC Office of State Fire Marshal interpretation, NCRC R409.5 closed crawl space moisture control and H-3 licensure: ducting supply air from the home's AC into a closed crawl space, or designing it as conditioned space, requires an H-3 heating license; a standalone crawl space dehumidifier does not.
• Wake County Permits and Inspections FAQ: a mechanical/HVAC permit is required for installation, extension, relocation, replacement and general repair of any heating, air-conditioning or venting system (applies in Wake County's own jurisdiction; Apex issues its own permits).

Code text and department procedures change; confirm current requirements with the jurisdiction before work starts.