If you’re planning an HVAC upgrade, home renovation, or system repair, understanding the cost of ductwork is critical. HVAC ductwork ensures your heating, ventilation, and air conditioning systems distribute air efficiently throughout your home.

But when modifications are needed, knowing how much ductwork costs, the factors affecting pricing, and potential hidden expenses is key. This guide provides a detailed look at ductwork installation cost, duct modification, duct replacement cost, and related services in 2025.

Understanding HVAC Ductwork

The air duct system in a house serves as the pathways for conditioned air from your HVAC unit to every room. There are typically two main types of ductwork:

• Supply ducts that deliver hot or cold air to rooms.
• Return ducts that pull air back to the HVAC system for reheating or cooling.

Modern homes may also have flex ducts, metal ducts, or fiberboard ducts. Over time, ductwork may require repairs, replacement, or modifications such as adding vents to existing ductwork.

Proper ductwork installation ensures energy efficiency, improved airflow, and consistent indoor temperatures.

Common Types of Ductwork Modifications

Here are the most common duct modifications homeowners or contractors may consider:

1. Adding a Vent to Existing Ductwork – If certain rooms are poorly heated or cooled, adding a vent can help balance airflow. The cost to add a return air vent usually depends on the duct type, accessibility, and labor rates.
2. Duct Work Replacement – Aging ducts may need to be replaced to improve HVAC efficiency. Duct replacement cost depends on duct material, home size, and whether you are installing new air ducts or reusing existing ducts.
3. Repairing or Replacing Air Conditioner Return Air Ducts – Return air issues can reduce system efficiency. AC return vent cover replacement or duct repair may be required.
4. Installing New Ductwork for HVAC Upgrades – When adding a central air unit, cost to install central air with ductwork includes both the HVAC system and full duct installation.
5. Ducting Modification for Remodeling – Renovations often require relocating ducts or adjusting their layout. Duct modification can involve cutting new pathways or adding plenum boxes.

Factors That Affect HVAC Ductwork Costs

Several factors influence how much does ductwork cost, including:

1. Duct Material – Common materials include sheet metal, flex duct, or fiberboard. Flex duct cost is usually lower, while metal ducts are more durable but expensive.
2. Home Size and Layout – Larger homes or multi-story houses require more ductwork, affecting ductwork prices.
3. Accessibility – Installing or replacing ducts in the attic, crawl space, or walls can increase labor costs. For example, the cost to install ductwork in an attic is often higher than in an open basement.
4. Number of Vents and Registers – More supply and return vents increase costs. Replacing old heat registers or installing heating and air conditioning ductwork will add to labor and material expenses.
5. Extent of Modification – Simple vent additions are cheaper than full duct work replacement.
6. Labor Costs – HVAC duct installer fees vary by region. Hiring professional HVAC ductwork installation services ensures code compliance and safety.

Average Costs of Ductwork Modification

Here’s a breakdown of average ductwork costs in 2025 for common scenarios:

The cost to install HVAC systems with ductwork or replace ducts is highly variable depending on materials, home layout, and contractor rates.

Cost to Replace Ductwork

When deciding how much does it cost to replace ductwork, consider both material and labor:

• Sheet Metal Ducts: $10–$20 per linear foot.
• Flex Ducts: $6–$12 per linear foot.
• Labor: $50–$100 per hour on average, depending on complexity.

Additional costs may include plenum box replacement, vent ductwork modifications, and return air duct adjustments. A complete duct work replacement ensures optimal airflow and HVAC efficiency.

Cost to Install HVAC Ductwork

Installing ducts as part of a new HVAC system includes air duct installation cost, duct installation cost, and sometimes duct armor cost for insulation.

Average estimates:

• Small homes: $1,500 – $3,500
• Medium homes: $3,500 – $6,000
• Large homes: $6,000 – $10,000+

Professional HVAC ductwork installation services ensure proper layout, correct sizing, and airtight connections, reducing energy loss.

Problems Associated With Bad Ductwork

• Uneven heating and cooling throughout the home
• Higher energy bills due to air leaks and poor airflow
• Reduced indoor air quality from dust, allergens, and contaminants entering ducts
• Increased strain on the HVAC system, leading to frequent breakdowns
• Excessive noise such as whistling, rattling, or banging from loose or undersized ducts
• Moisture buildup and mold growth inside ductwork
• Air pressure imbalances causing drafts and inconsistent airflow
• Pests, insects, and debris entering through gaps or damaged duct sections

DIY vs. Professional Installation

While some homeowners attempt DIY air duct install, professional installation is recommended for:

• Accurate sizing of supply and return ducts.
• Correct how to add vent to existing ductwork techniques.
• Proper sealing of joints to prevent energy loss.
• Avoiding code violations or safety hazards.

Hiring certified HVAC duct installers may cost more upfront but saves money by improving energy efficiency and reducing future duct work repair near me calls.

Common Ductwork Modification Projects

Here are examples of typical modifications:

1. Adding a Vent to Existing Ductwork

• Cost: $100 – $350 per vent
• Reason: Balances airflow in rooms that feel too hot or cold.

2. Replacing Old Heat Registers or AC Return Boxes

• Cost: $50 – $200 per register/box
• Reason: Improves airflow and energy efficiency.

3. Converting Window AC to Ducted System

• Cost: $3,000 – $7,000
• Reason: Replaces inefficient window units with full ducted heating and air conditioning ductwork.

4. Flex Duct Replacement

• Cost: $6 – $12 per linear foot
• Reason: Flex ducts degrade faster than sheet metal and may restrict airflow.

5. Plenum Replacement

• Cost: $400 – $1,200
• Reason: Connects HVAC system to ducts; damaged plenums reduce efficiency.

Tips to Save on Ductwork Costs

• Seal leaks in existing ducts before full replacement.
• Use flex ducts in difficult-to-reach areas.
• Bundle ductwork installation with HVAC system replacement to save on labor.
• Compare quotes from multiple HVAC duct installers to get the best pricing.
• Consider partial duct replacement if only certain areas need attention.

Frequently Asked Questions

How much does it cost to change ductwork?

The cost varies based on project size, materials, and labor. Minor repairs or small modifications range from $150 to $500, while adding a vent can cost $100 to $350 per vent. Partial duct replacement may cost $1,500 to $5,000, and full replacement can reach $8,000. Material type, home size, and accessibility all affect pricing, and professional HVAC ductwork installation ensures efficiency and code compliance.

What is the 2-foot rule for ductwork?

The “2-foot rule” suggests keeping duct runs within 2 feet of walls or ceiling drops to reduce airflow resistance, minimize energy loss, and simplify installation. Following this ensures balanced airflow and improves HVAC efficiency.

Is duct replacement expensive?

Yes, duct replacement is costly due to labor-intensive work, material prices, and accessibility challenges. Proper sizing and integration with the HVAC system are also required to maintain efficiency, making full replacement range from $2,000 to $8,000 in most homes.

How does ductwork affect HVAC system cost?

Ductwork impacts both installation costs and system efficiency. Poor or leaky ducts reduce HVAC performance and increase energy bills, while well-installed ducts optimize airflow, may reduce the size of the HVAC unit needed, and help avoid future repairs.