> By: The Cooling Company > Published: 2025-12-29 > Last updated: 2025-12-29
Replacing attic ductwork removes leaky, damaged runs and installs correctly sized, sealed, insulated ducts. New ducts cut energy waste, improve comfort, and reduce equipment runtime. Choose replacement when ducts are crushed, moldy, or lose over 15–20% of airflow. Always require testing and a Manual D layout from your contractor. This article summarizes the work, cost, materials, and questions to.
Key Takeaways
- Replace attic ducts when they are crushed, disconnected, or lose more than 15–20% of system airflow.
- Require Manual D sizing, mastic or UL 181 tape, and R-6 or higher insulation on attic ducts.
- Get at least two written bids that show pre/post leakage testing and room-by-room airflow.
- Ask about permits, warranties, and expected run-time or energy savings estimates.
Source: ASHRAE Technical Resources
When should I replace attic ductwork?
Many homes have attic ducts that show obvious problems. Sagging flex, crushed trunks, and tape at many joints are common signs of failure. When you see that damage, replacement often outperforms repeated repairs. Repeated repairs can delay a full fix and increase long-term costs.
Decide between repair and replacement by measuring leakage and airflow. If ducts leak more than 15–20% of fan flow, or if trunks are crushed or moldy, replacement usually gives the best long-term value. Ask for a duct blaster test to document the condition. Contractors should include clear before figures in writing.
A contractor should present before-and-after test numbers. Those numbers prove whether the work fixed the real problem. Always require a Manual D layout with the bid so you can check sizing and expected airflow improvements. Do not accept vague promises about percent savings without measured data.
What signs show ducts need replacement?
Look for visible damage first. Tears, sagging flexible runs, duct sections held together with tape, or insulation that is wet or moldy all point to major problems. Also check for animal damage and crushed trunk sections. Visual problems often correlate with high leakage.
Listen and feel at the registers. Whistling, large temperature swings, or weak flow at vents after routine system service mean leaks or poor routing. Rooms that stay hot or cold compared to the rest of the house are key clues to attic duct trouble. Document problem rooms and times when the issue is worst.
Can repairs beat full replacement?
Small leaks and loose boots are often fixed with mastic or UL 181 tape. Re-supporting flex and sealing a few joints can restore acceptable airflow for a low cost. These fixes work when ducts are otherwise properly sized and routed and when damage is limited to small openings.
However, repairs are a poor choice for crushed trunks, rodent damage, or mold. Those conditions shorten the life of any local fix. Full replacement corrects routing, sizing, and seal in one scope and reduces future callbacks. Ask your contractor to explain the expected life after a repair versus a replacement.
How do leaks affect energy bills?
Leaky attic ducts send conditioned air into a hot, unconditioned space. That makes the HVAC run longer to reach thermostat setpoints. Longer runtimes raise energy bills and add wear to the equipment. Leaks also reduce comfort and make zoning problems worse.
Field studies often show attic duct leakage accounts for significant losses. The exact savings vary by home. Large leaks can easily cost hundreds of dollars a year in a typical U.S. Home. Measure leaks to estimate local savings and use those figures to compute payback on replacement work.
What does replacement involve?
A proper replacement starts with measurement and a plan. Contractors should size ducts using ACCA Manual D and consider the air handler static pressure limits. A clear plan shows trunk and branch paths, fittings, and access needs. Plans also list materials, insulation R-value, and sealing methods.
Installation removes damaged runs and installs new trunks and branches. Technicians seal all joints with mastic or UL 181 tape and insulate ducts to the required R-value. Finally, testing and balancing confirm that each room gets the target airflow. Post-install documentation should include leakage and airflow numbers.
Work may include attic prep. That can mean creating a temporary walkway, clearing insulation from the work area, and adding rodent screens or duct protection. These steps protect the work and extend the life of the new ducts. A good scope will list attic protection steps and cleanup obligations.
What steps are in an attic duct replacement?
Begin with an on-site inspection and measurements. A technician should record static pressure at the blower, measure register flows, and map existing branch runs. That data drives the Manual D layout and material list. The pre-test should be provided in writing.
During installation, crews remove old duct sections and install the trunk first. Branches follow, with careful support at recommended intervals. After sealing, the team insulates and seals access points. Final tests show leakage and register flows. Expect a final report with before-and-after numbers.
Which duct materials are installed?
Common choices include galvanized metal trunks, insulated rigid ducts, fiberglass duct board, and insulated flex for short branches. Metal trunks leak less and handle higher airflow. Insulated flex works for tight branch runs when installed correctly and supported properly.
Material choice depends on budget and attic access. A robust approach uses metal for trunks and quality insulated flex for short branches. Avoid cheap flex installed sagging and unsupported, as it reduces airflow and raises static pressure. Ask bidders to list brand names and insulation type in the bid.
How is duct sizing and layout determined?
Use ACCA Manual D to size ducts for the desired room airflow. Manual D balances velocity, pressure drop, and noise against the blower’s static pressure limit. Proper sizing avoids high static pressure that reduces system airflow.
Ask the contractor to share a Manual D layout or a written explanation. Confirm the design matches your air handler’s fan curve and your room-by-room load needs. That step prevents undersized runs that lead to chronic comfort complaints and higher runtime.
How much will it cost?
Price depends on house size, attic layout, materials, and how much demolition or attic prep is needed. Minor repairs often cost a few hundred to a few thousand dollars. Full trunk-and-branch replacements commonly run higher. Transparent bids list labor, materials, testing, and permit fees.
Expect simpler partial replacements to start near $500 to $3,500. A full replacement for a medium-sized home commonly ranges from $6,000 to $12,000. Large or complex homes can cost more, depending on access and scope. Use measured pre/post leakage and airflow data to estimate payback.
Always compare itemized bids that list labor, materials, testing, and permit fees. Use measured pre/post leakage and airflow data to estimate payback and energy savings instead of trusting broad percentage claims alone. Ask for the math behind any claimed savings.
What are typical cost ranges?
Partial repairs and short-run replacements can be affordable. Homeowners often see quotes in the low thousands for limited work. Full replacements with sheet metal trunks and new branches cost more due to labor and materials. Expect variance by region and company.
A midrange job for an average house often falls between $6,000 and $12,000. High-end jobs with extra insulation, attic walkway protection, or complex routing push higher. Ask bidders for a breakdown to compare apples-to-apples. Check whether permits are included in the price.
How do materials affect pricing?
Sheet metal trunks increase material and labor costs but reduce leakage and last longer. Insulated flex is cheaper and faster to install but requires careful handling to avoid sag and creases that reduce flow. Labor skill affects outcome as much as material choice.
Upgrading insulation thickness raises material cost. Higher R-values help in cold climates and can be required by local code. Factor labor for sealing and testing into the total price when evaluating bids. A low bid that skips testing is often a false economy.
Can replacing ducts save 20 to 30 percent per DOE?
DOE and research labs report that badly leaking attic ducts can lose roughly 20–30% of system air in many homes. Replacement or sealing can cut a large share of that loss in severe cases. Savings vary by home, climate, and usage patterns.
If ducts already leak only a little, your ROI will be smaller. Require a contractor to estimate saved kWh or therms based on measured leakage and your local utility rates. That data helps you compute realistic payback and decide if replacement is warranted.
Are there rebates available?
Many utilities and state programs offer incentives for duct sealing, insulation, or whole-home efficiency. Rebates vary by location and program rules. In some areas, incentives offset a large share of cost for qualifying work. Ask bidders to include potential rebates in the bid.
Ask bidders to check utility programs and include eligible rebates in their bids. A contractor familiar with local incentives can help submit paperwork and speed rebate payments to homeowners. Keep copies of invoices and test reports for rebate applications.
Which materials and methods are best?
Choosing the right materials depends on attic access, budget, and performance goals. Metal trunks for main flow and well-installed insulated flex for short runs form a good mix. Prioritize sealing and sizing over material alone. Installation quality is the key driver of long-term performance.
Installation quality matters most. Even the best materials fail when joints are left unsealed or flex ducts are crushed. Demand mastic or UL 181 tape for all joints and post-install testing to confirm leakage and flows. Ask for a workmanship warranty and documented test results.
Consider long-term durability when choosing materials. Metal trunks resist pests and compressive damage. Properly supported flex can perform well for branches, but expect shorter life and more careful installation practices. Confirm that the contractor uses rated insulation and proper fasteners.
Is insulated rigid duct better than flex?
Insulated rigid ducts have a smooth interior that reduces friction and pressure drop. They resist kinks and rodent damage and often last longer. That makes them ideal for long trunk runs feeding many branches.
Rigid ducts cost more and can be harder to install in tight spaces. Insulated flex performs well for short branches when it is kept straight, stretched, and supported. The key is correct installation, whatever material you choose. Inspect supports and bends carefully.
When should sheet metal be used?
Use sheet metal for the main trunk and high-flow sections. It holds shape, seals tightly with mechanical connections, and handles higher velocity without collapse. This reduces leakage and improves long-term performance.
Pair a sheet metal trunk with insulated flex branches where routing needs demand flexibility. That approach balances cost, durability, and airflow performance across the whole system. Look for screws and mastic at sheet metal joints rather than just tape.
How does R value affect attic performance?
R-value measures thermal resistance. In unconditioned attics, ducts should be insulated to at least R-6. Colder climates or local codes often require higher R-values, such as R-8 or R-11. Ask bidders to state the R-value they will install.
Higher R-values cut heat gain in summer and heat loss in winter. Insulation reduces temperature change but does not seal leaks. Combine adequate R-value with airtight sealing for the best energy savings. Verify installed insulation thickness in photos or on-site.
How do I choose a contractor?
Choosing the right contractor makes the biggest difference in results. Prefer firms that size ducts with Manual D, seal with mastic or UL 181 tape, and include duct blaster testing in their scope. Get itemized bids and references. Quality contractors provide documentation and warranties.
Avoid bidders that refuse testing or offer vague scopes. A clear proposal lists materials, R-value, sealing methods, and testing steps. Check licensing and insurance. Verify whether crews are employees or subcontractors and whether the company provides a workmanship warranty.
Look for documented warranties and post-install testing. A quality contractor provides a workmanship warranty and will return to re-test if leakage or airflow issues appear inside the warranty window. Keep all test reports and photos for warranty claims.
What qualifications should a pro have?
A qualified pro carries the correct HVAC license for your local jurisdiction. They should also have general liability and workers’ compensation insurance. These items protect you if damage or injury happens during the job.
Experience with attic ductwork and Manual D designs is important. Ask how many similar projects the company has completed and whether they provide testing and balancing as a standard part of the job. Request references and photos of completed work.
Should I hire NATE certified technicians?
NATE certification shows the technician passed standardized HVAC tests. Hiring NATE-certified techs often improves diagnostics and installation quality. Certification alone is not enough, but it is a strong positive sign of competency.
If you live outside our area, use the NATE website to find certified technicians locally. Pair certification with references, detailed bids, and testing to ensure quality work and reliable outcomes. Certification combined with testing is the best signal.
How do I verify HVAC contractor insurance?
Ask the contractor for a current Certificate of Insurance. Confirm it lists general liability and workers’ compensation. Make sure coverage is adequate for the project size and scope. Do not accept verbal claims of coverage.
Call the insurer if you need confirmation. Written proof protects you if there is property damage or injuries during the job. Keep a copy of the certificate with your contract and bid paperwork for your records.
What questions should I ask bidders?
Request a Manual D layout, a materials list, and a sealing plan. Ask whether they will use mastic or UL 181-rated tape and what R-value they will install. Confirm permit handling, testing, and warranty terms. Specific questions reveal how thorough the contractor will be.
Also request pre/post duct blaster tests and a room-by-room airflow report. Ask for references and before/after photos from similar attic duct projects. Use the answers to compare bids on facts, not price alone. Be wary of low bids that omit testing.
How are airflow and static pressure tested?
Techs use a manometer to measure static pressure at the air handler. They use flow hoods or anemometers at registers to measure airflow. Duct blaster tests pressurize the duct system and measure leakage in CFM25. These tests provide objective measures.
These tests show how hard the fan works and how much air escapes. Use the data to plan repairs or replacements and to verify post-install improvements claimed by the contractor. Insist on written results in the final report.
Do contractors offer duct blaster testing?
Reputable firms include duct blaster testing with full replacements or offer it as an add-on. Pre- and post-install tests prove the work reduced leakage and increased delivered airflow. Test reports should be attached to the final invoice.
If a contractor refuses testing, treat that as a red flag. Objective test results are the best way to measure whether the job met its targets and whether your investment delivered real savings. Keep all test documents for future reference.
Request a free attic duct estimate
Getting an on-site estimate starts the process. Prepare basic home info and your comfort notes. An accurate estimate requires attic access and a look at the existing duct layout, insulation, and air handler location. The estimator will want to see problem rooms and any visible duct damage.
For Las Vegas area homeowners, The Cooling Company provides detailed attic duct inspections, Manual D-based designs, duct blaster testing, and itemized bids. The company serves Las Vegas, Henderson, and North Las Vegas and offers written warranties and post-install testing. Expect clear documentation.
Expect a contractor to ask about problem rooms, thermostat setbacks, and recent utility bills. Provide photos of attic access and any visible damage to speed the site visit and improve quote accuracy. Detailed pre-test data yields better estimates and clearer payback math.
How to prepare your home for an estimate?
Clear attic access so the estimator can enter safely. Make sure an adult is home to answer system history and comfort issue questions. Note which rooms are uncomfortable and when the problem appears. Photos of attic conditions help the estimator prepare.
Bring recent utility bills if available. Photos of attic access and visible duct damage help the estimator prepare. These steps let the contractor give a more accurate on-site estimate and testing plan. Good documentation improves bid quality and reduces surprises.
Call to action: book a licensed HVAC pro
Las Vegas area readers: call The Cooling Company at 17029308411 to schedule a free attic duct estimate. The Cooling Company will perform Manual D design, duct blaster testing, and provide a detailed, itemized bid. Service areas include Las Vegas, Henderson, and North Las Vegas.
Outside the Las Vegas area: find NATE-certified technicians at the NATE website and ask for the same scope. Request Manual D sizing, mastic or UL 181 sealing, R-value insulation, pre/post duct blaster testing, and a written workmanship warranty. Use the same checklist when comparing bids locally.
Call 17029308411 to get a clear, tested plan from The Cooling Company. Ask for pre- and post-test results, a room-by-room airflow report, and a written warranty to protect your investment.
About The Cooling Company
- Phone: 17029308411
Sources and compliance notes
This aspect deserves careful consideration as you evaluate your options. Understanding the details helps you make more informed decisions. Consulting with qualified professionals provides additional insights specific to your situation. Take time to consider how this information applies to your particular needs and circumstances. Making well-informed choices typically leads to better long-term outcomes and greater satisfaction.