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My AC Guy Says I Need All New Ductwork

Your AC guy says:

“You need all new ductwork.”

Maybe.

But that’s a big, expensive job, so we’d like to know what’s actually wrong with the ducts.

Because one bad duct doesn’t mean the other fifteen suddenly need to be ripped out.

When Does Ductwork Actually Need Replacement?

There are legitimate reasons.

We may recommend replacing some or all of a duct system when we find:

  • badly deteriorated or damaged ducts
  • collapsed or torn flex duct
  • failing insulation or vapor barriers
  • widespread leakage
  • ducts that are significantly undersized
  • a poor duct design that can’t properly move the required airflow
  • wet or contaminated insulated ductwork that can’t reasonably be restored

EPA guidance specifically notes that wet or mold-contaminated insulated duct material may need replacement rather than cleaning.

But that’s very different from:

“Your ducts are old. Replace everything.”

Sometimes You Only Need Part of It

This is especially common.

Maybe the main supply trunk is deteriorated.

Maybe three flex runs are crushed.

Maybe one return is undersized.

Maybe a connection came apart in the attic.

Fix those problems.

We’ve done plenty of duct jobs where we replace the failed sections and leave perfectly serviceable ductwork alone.

Full replacement isn’t automatically the answer just because part of the system has a problem. Targeted repair or partial replacement can be appropriate when the remaining ducts are sound.

What Should You Ask?

Ask:

“Can you show me why the ducts need to be replaced?”

That’s a very reasonable question.

If we’re recommending thousands of dollars worth of ductwork, we should be able to show you:

Here’s what’s damaged.

Here’s what’s undersized.

Here’s what’s leaking.

Here’s why repairing only this section will—or won’t—solve the problem.

Pictures from the attic help too.

The Klein Answer

Yes, sometimes a house really does need all new ductwork.

We’ve recommended it.

We’ve installed it.

But we’ve also repaired one duct, replaced one trunk, added return air, replaced only one side of a duct system, and left everything else alone.

The recommendation should match the problem.

So if somebody tells you:

“You need all new ducts.”

Ask them to show you why.

If the whole system is shot?

Replace it.

If three ducts are bad?

Why are we replacing twelve?