Rust and More: The Consequences of Moisture in Your Air Ducts

D.P. Taylor
Written by D.P. Taylor
Updated March 2, 2022
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  • HVAC air ducts must be kept dry and clean.

  • If left unchecked, moisture can cause the air ducts to rust.

  • Moisture can cause a host of other issues from mold to water damage.

  • Contact a professional to inspect your system and recommend a course of action.

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Your heating, ventilation, and air conditioning (HVAC) system needs air ducts that are dry and clean. When moisture finds its way into your air ducts, it can cause a slew of problems that range from uncomfortable to downright dangerous.

For one, mold spores can spread through your home and into your clothing and furnishings, causing a decline in indoor air quality and possibly causing health problems. Moisture can also damage your roof, walls, insulation, and ceilings.

As a result, it's essential to deal with this issue. Keep reading for ways to spot, prevent, and treat excess moisture and rust in your air ducts.

Moisture in the Air Ducts: Where Does It Come From?

So where is all this moisture coming from? It could be from any number of sources. For example, a pipe may burst and cause water to leak into the ducts. Or, your roof might spring a leak. Sometimes, ducts mounted in your roof won't have a watertight seal.

Also, condensation may build up on the cooling coils in your air conditioning system if the air in the HVAC system is colder than the air around it. This can result in moisture making its way into the air ducts.

Once moisture starts building up, mold can form and your ducts will start to rust. Mold spores can start growing within as little as 48 hours, so it’s important to act fast. As long as there is a wet environment and an organic food source, mold can grow pretty much anywhere.

Common Problems Moisture and Rust Can Cause in Air Ducts

Once your ducts rust and mold spores form, the spores can quickly spread throughout your home, landing on clothing, carpets, and furnishings. Obviously, this is not good for your indoor air quality, and the developing mold can cause health issues for everyone who lives there. Itchy eyes, nausea, and difficulty breathing are a few signs you may have mold in your air ducts. If left unchecked, the rust will force you to replace the air ducts.

But it’s not just mold development that is a problem in this situation. Moisture in the air ducts will compress the insulation, which will be less effective, leading to higher utility costs and energy loss.

High moisture levels will raise the humidity levels in your home. This will make your home less comfortable, and it could damage parts of your home like wood flooring or paint. It also may cause unpleasant odors to emerge.

Finally, excess moisture in the air ducts can result in water damage to your roof, walls, and ceiling. And this excess moisture can cause decay in other home materials and even threaten the structure's integrity if it goes unchecked for a long time.

What Can You Do to Fix a Duct Rusting Problem?

Man opening air duct cover
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A large part of tackling duct-related rust is taking steps to prevent it from forming in the first place. It is recommended that you clean your ducts every three to five years. This can help thwart standing water, mold, dust, and other debris that can affect your heating and cooling system’s functionality down the line. 

Here are a few ways you can stop condensation from forming rust in your air ducts:

  • Purchase a dehumidifier for your home

  • Clean your vents regularly and change out air filters

  • Clear out vents with restricted airflow

  • Wrap your ductwork to prevent condensation from forming

  • Keep ducts with enough space between them so air flows freely

If you suspect that the excess moisture buildup in your air ducts has already produced rust, you need to take action right away to prevent the development of mold and further rust damage to your ducts. 

Contact an HVAC professional near you to come out and take a look at your air ducts. They can tell you how bad the problem is, recommend a course of action—such as an extensive cleaning of your air ducts—and provide a quote for repair. The sooner you address the problem, the better.

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