If you were told your ductwork needs to be replaced, the recommendation should come with proof. That means photos from your attic, static pressure readings, the specific leak or crush points, the condition of the duct insulation, and any sizing problems the technician found. If the tech cannot show you those things, ask for them before you agree to the work. Many duct problems can be fixed with repairs or sealing, so this post covers what each piece of evidence should look like, when repair is enough, and what drives the scope of a replacement.
What should a technician show you before recommending new ducts?
Ducts are mostly out of sight. They sit in the attic, in a chase, or under the floor. That makes them easy to recommend and hard for you to check. A good recommendation closes that gap with evidence you can see.
The evidence checklist
Before you sign anything, you should have:
- Attic photos of the actual runs in your home, not stock pictures.
- Static pressure readings taken at the air handler, with a short explanation of what they mean.
- A list of leak or crush points, with where each one is.
- Notes on insulation condition, including torn jackets, wet spots, or sweating.
- Any sizing problems, such as rooms that get too little air or returns that are too small for the system.
Signs the inspection was too quick
If the inspection felt too quick, it probably was. Checking ductwork means getting into the attic, looking at the supply and return runs, and testing how the system moves air. A walk past the thermostat and a glance at the vents is not enough to justify a full replacement.
The takeaway: A replacement recommendation without photos, readings, and specific problem locations is a guess, so ask for the evidence first.
What should attic photos of your ductwork show?
Photos are the simplest way to see what the tech saw. Ask for them even if you plan to go up and look yourself. Jacksonville attics get very hot in summer, and the photos let you look closely without the heat.
Problems the photos should capture
- Crushed or kinked flex duct. Runs that were stepped on, pinched by framing, or bent too sharply choke airflow.
- Disconnected or loose runs. A duct that has pulled off a boot or a plenum dumps cooled air into the attic.
- Sagging runs. Flex duct that hangs between supports restricts air and can collect condensation.
- Torn or brittle outer jackets. Exposed insulation or a cracked vapor barrier lets humid attic air reach the cold inner liner.
- Water stains, sweating, or mold-like growth on ducts, boots, or the drywall around supply registers.
- Pest damage. Rodents chew duct jackets and nest in insulation.
One problem or many
One damaged run is a repair. Replacement starts to make sense when damage is spread across most of the system, or ducts are failing in many places at once. The photos should make that difference clear.
The takeaway: Photos should show whether you have a few damaged spots or a system failing throughout, because that decides repair versus replacement.
What does static pressure tell you about your ducts?
Static pressure is the resistance your blower works against to push air through the ducts, filter, and coil. A technician measures it with a manometer at the air handler. It is one of the few hard numbers that tells you whether the duct system fits the equipment.
Comparing the reading to the rating
Every air handler has a rated total external static pressure, listed by the manufacturer. On many residential systems that rating is typically around 0.5 inches of water column. If the measured number is well above the rating, the ducts, filter, or coil are restricting airflow.
Symptoms of high static pressure
- Rooms that never cool down, or an AC unit that can’t keep up in July.
- Loud air at the registers or a whistling return.
- A frozen coil or short equipment life.
What to ask the tech
Ask the tech to write down the readings and the equipment rating side by side. Also ask what they ruled out. A clogged filter or a dirty coil can push static pressure up on its own, and those are not duct problems.
The takeaway: Get the measured static pressure and the manufacturer’s rating in writing, and confirm the filter and coil were ruled out.
How do insulation, humidity, and duct size affect the recommendation?
Insulation and sweating ducts
In Northeast Florida, duct insulation matters as much as the duct itself. Cold air moves through ducts that sit in a hot, humid attic. If the insulation is thin, torn, or compressed, the outside of the duct sweats. That moisture drips onto drywall, feeds mold, and adds humidity back into the house.
If your home feels damp even with the AC running, read why a house can feel sticky at 74 degrees. Leaky or sweating ducts are one common cause.
The recommendation should say whether the insulation is damaged in spots or failing across the system. Flex duct jackets are printed with an insulation rating. Older ducts may have a lower rating than current energy code calls for in an attic.
Sizing problems
Sizing is the other piece. Ducts can be in good physical shape and still be the wrong size. Common signs:
- One or two rooms, often a bonus room or a far bedroom, stay warm.
- The return is too small, so the system gasps for air.
- A new system was installed with larger capacity, but the old ducts stayed.
How sizing should be calculated
If sizing is the reason for replacement, ask how it was calculated. Duct design is usually done with a load calculation and a duct design method, often referred to as Manual J and ACCA Manual D. You should get room-by-room reasoning, not a general statement that the ducts are too small.
The takeaway: Insulation and sizing claims should be specific to your attic and your rooms, with the calculation method named.
Ductwork repair vs replacement: which do you need?
Full replacement is not the only answer. Many duct problems can be fixed in place.
| Problem found | Often fixed with | Replacement more likely when |
|---|---|---|
| A few loose connections | Reattaching and sealing with mastic | Connections are failing throughout the system |
| One crushed or kinked run | Replacing that single run | Many runs are crushed or poorly routed |
| Leaks at the plenum or boots | Sealing seams and boots | The plenum or duct board is deteriorated |
| Torn jacket in a few spots | Repairing or re-wrapping those sections | Insulation is brittle or wet across the attic |
| One weak room | Adding or resizing a single run | The whole layout cannot deliver the air the system needs |
Where duct cleaning fits
Duct cleaning is a separate service. It removes dust and debris but does not seal leaks or fix crushed runs. Our page on air duct cleaning and duct services in Jacksonville explains what cleaning handles and when other duct work is needed. The EPA also has guidance on when air duct cleaning makes sense.
When a mini split is worth comparing
Your ductwork may still be in decent shape while you add space or try to cool one problem area. In that case, a ductless mini split may be worth comparing against new duct runs.
The takeaway: Limited damage usually calls for repair or sealing, and replacement fits when problems run through the whole system.
What drives the cost of a ductwork replacement?
When duct quotes look very high, the scope is usually the reason. Two homes with the same square footage can need very different jobs. Ask the company to explain each of these for your house.
Scope factors to ask about
- Attic access. A roomy attic in a single-story Orange Park ranch is a different job than a tight, low-pitched attic in an older St. Augustine home. Small hatches, low clearance, and deep blown-in insulation slow the work.
- Home layout. Two-story homes in Ponte Vedra or Fleming Island often have runs in chases between floors, a second system, or ducts serving a bonus room over the garage. Long, branching runs take more material and labor.
- Duct material. Flex duct, rigid duct board, and sheet metal are installed differently. Some older homes have a mix, and swapping one type for another changes the plan.
- Number of supplies and returns. Adding returns or relocating registers means cutting drywall and ceilings.
- Damage removal. Moldy or pest-damaged ducts and insulation may need extra removal and cleanup.
- Permits and HOA rules. Duct replacement often requires a permit, and some communities have rules about work schedules or contractor access. Ask whether the quote covers permitting.
What the written scope should list
A written scope should list what is being replaced, what is staying, and what materials are being used. That is what lets you compare quotes fairly.
The takeaway: Compare duct quotes by their written scope, not just the total.
Do you need new ductwork when you replace your AC?
If you are also replacing the AC or heat pump, ask whether the existing ducts were checked against the new equipment. A new system on mismatched ducts can underperform. Our AC replacement and installation page covers how system replacement is planned, and our heat pump services page covers heat pump systems.
Not every replacement needs new ducts. The recommendation should say which applies to your home and why.
The takeaway: A system replacement quote should state whether your current ducts were tested against the new equipment.
Should you get a second opinion on ductwork replacement?
A second opinion on ductwork is reasonable. That is especially true when the first visit felt like a sales pitch or the decision felt rushed.
How to make a second opinion useful
- Bring the photos and readings from the first visit.
- Ask the second company to check the same points.
- Compare the two findings side by side.
If both find the same problems, you can move ahead with more confidence. If they disagree, the evidence shows you where.
The takeaway: A second opinion works best when both companies check the same runs and take the same readings.
What to expect when you have Great Dane inspect your ducts
Great Dane Heating & Air is a family-owned company in Jacksonville, Florida license CAC036942. We inspect ductwork in Jacksonville, Orange Park, Fleming Island, Ponte Vedra, and St. Augustine and show you what we find.
What a good duct recommendation includes
- Photos of your actual duct runs, supply and return.
- Static pressure readings next to the equipment rating.
- A list of leak, crush, and insulation problems with locations.
- A clear call on repair, sealing, partial replacement, or full replacement, with the reason.
- A written scope listing what is replaced, what stays, and the materials.
You can request a free estimate for a duct inspection or a second look at a quote you already have.
The short version
A ductwork replacement recommendation should be backed by photos, readings, and specific problem locations. Many duct problems can be repaired or sealed. When replacement is the right call, the written scope should explain why and list exactly what is being done.
If you were told your ductwork needs to be replaced and want to see the evidence, contact Great Dane Heating & Air to schedule an inspection. Estimates are free.
Frequently asked questions
Is flex duct or sheet metal better for a Florida attic?
Both are used in Jacksonville-area homes, and flex duct is common in attics. Sheet metal holds its shape and resists crushing, but it takes more labor to install. With either material, the install matters most: runs should be short, supported, sealed at every connection, and well insulated.
How long does a ductwork replacement take?
It depends on the size of the home, attic access, the number of systems, and whether registers or returns are being moved. Ask the company for a written schedule. It should note any drywall or ceiling work and when your AC will be off.
Can I use my AC while the ducts are being replaced?
Usually not while ducts are disconnected, since the system has nowhere to send the air. Ask the crew when the system will be off and back on. In summer, plan for the house to warm up during that window, and keep pets and anyone sensitive to heat comfortable.
Can I check my own attic ductwork safely?
Go up early in the morning before the attic heats up, and bring a good light and your phone camera. Step only on joists or a walkway, never on ducts or bare drywall, and stay clear of wiring. If access is tight or you feel unsteady, ask for photos instead.
What can I do about sweating ducts until they are fixed?
Keep a clean filter in the system and watch ceilings near supply registers for stains or drips. Very low thermostat settings make the ducts colder, which can add to sweating. Have the ducts checked soon, since ongoing moisture can damage drywall and feed mold.
Is mold on my ducts a sign they need to be replaced?
Not always. Growth on the outside of a duct usually points to condensation from poor insulation or leaks, and that cause has to be fixed. Flex duct or duct board with contamination inside the insulation is often replaced rather than cleaned, so ask the technician which situation you have.
How do you know if new ductwork is working?
Ask for static pressure readings after the job and compare them with the readings taken before. The rooms that were problems should cool more evenly, and registers should not whistle. Ask for photos of the finished runs and connections in the attic as well.
