Should I Clean or Replace My Air Ducts?

Worker holding dirty air duct vent
Can air ducts get too dirty for ac cleaning? Angie Hicks talks about air duct replacement costs.
Dear Angie: We have had a problem with dust in our 2-year-old house. We had someone come and inspect our air ducts to see if they needed to be cleaned. His inspection revealed that we had a lot of dust in our coils and air ducts. He said the most likely reason for the amount of dust is that the builder ran the ac cleaning unit without air filters in place.

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He recommended that we clean the coil, remove and clean the blower and replace at least 25 air ducts. He recommended replacing the air ducts rather than cleaning them because the air ducts were made of plastic and they were difficult to clean properly. The estimated cost is more than $10,000 and could be more for the air duct replacement cost. Is it common to replace your air ducts because they are too dirty to clean properly? – Name and city withheld by request

air duct technician using hose to clean air duct
Investigate air duct cleaning companies before hiring to avoid unscrupulous contractors. (Photo courtesy of Marion White)

Dear Anonymous: There are a number of factors that determine whether you can clean or need to repair your air ducts. The first is the type of ductwork you have. In most cases, most types of ductwork can be easily cleaned, especially in a newer home.

Metal ductwork with no interior lining can almost assuredly be cleaned. If the ducting is constructed of fiber board, though, it cannot be cleaned as easily. If the contamination is severe, it likely needs to be replaced.

However, you say your ducts are made of plastic, which I’m inclined to believe means you have flexible ductwork. Flex ductwork is typically made of a wire coil covered by a thin, flexible plastic wall and wrapped in insulation and foil backing. If the flex ducts only have dust or debris, they should be able to be easily cleaned by a qualified professional with the right tools. However, if the flex ducts have mold growth — depending on the level of contamination — they could need to be replaced.

Before you agree to an air duct cleaning — or decide to replace instead, if that’s necessary — it’s important that you find the source of the dust. Every duct system has some residual dust, regardless of how well it is cleaned, but because your home was only recently constructed, it shouldn’t need a duct cleaning so soon.

How to tell if your air ducts need to be cleaned
However, there are exceptions to that. If the builder ran the heating and cooling system during the construction phase, that could certainly be at the root of the issue. It’s also possible the entire HVAC system needs to be better sealed. Air leakages can draw additional dirt and dust into the system. Hire a contractor to conduct a blower door test to help you determine exactly where any leaks could be occurring.

It all really comes back to how well the system was installed. Some reputable air duct cleaning companies have told me they’ve seen new houses where the systems and ducts are so poorly done that they require re-engineering and a major renovation, but few recommend a total replacement. Unfortunately, some companies use scare tactics, like saying there is mold present, to oversell unnecessary air duct replacement or cleaning.

My advice is to do your research and find at least two more companies that have a solid reputation and specialize in air duct systems. Many companies offer multiple services, including carpet and chimney cleaning, but you really need someone who focuses solely on air duct systems and is in good standing with the National Air Duct Cleaners Association. Look for credible online reviews and testimonials from clients to get a feel for how these companies resolve issues like yours and ask for detailed estimates so you can compare apples to apples.