Does Metal Ductwork Rust?

Yes, there are certain factors that can contribute to rusting on metal ductwork. This can be caused by condensation or old ductwork that hasn’t been maintained.

The naturally hot and dry climate within a duct naturally makes it difficult for mould to thrive. But if a duct becomes unsealed, or there is a dramatic change in the duct’s environment that causes humidity, mould can grow within it.

What happens to a duct if it grows mould?

If ducting has mould growing within it, it can present a dangerous health hazard as the spores can spread amongst the whole ventilation system and the dwelling it operates in. As a result, you may have to completely replace the venting system/ ductwork depending on the severity.

Preventing rust in the ductwork

One of the key factors in preventing or delaying the onset of rust on your metal ductwork is ensuring there is no condensation appearing on the ducting.

You can stop condensation on metal ductwork most of the time, however, the only exception to this would be instances of dramatic temperature fluctuations that occur due to freak weather occurrences, a lack of electricity to power the ventilation system or a combination of both.

These occasions are extremely rare. But here are some things you can keep track of, to ensure your ducting does not develop condensation.

• Check your ducting for any leakage, is there holes? Are they sealed?
• Apply ducting insulation
• Use ducting tape on secure connections to further ensure their efficiency
• Check your ducting for rust, and/or condensation on the outside of the ductwork

Generally, the likelihood of metal ductwork growing mould is very low. However, this can happen if certain circumstances are met. A clean, sealed duct will present an environment where mould can’t grow, this changes with the introduction of dust & humidity.

Why else would my ducting need replacing?

Here are some key factors that would determine your ductwork being replaced without the intervention of an HVAC technician to check themselves.

• A reduced input/output (this can indicate a large amount of dust inside the ducting)
• Broken areas that allow air to escape, whether this is on the ducting pipe or the connecting joints
• Condensation on the ductwork
• If the ducting hasn’t been checked or worked on in years
• Mould in areas neighbouring the ducting (could be an indication to mould being within the ductwork.)

How long does metal ducting last?

Ducting generally has a maximum lifespan of 20-25 years, if it is well-maintained, regularly checked and insulated. Regardless, metal ducting degrades over time, this is due to the expansion and contraction of metal in response to local relative temperature, which fluctuates seasonally.

When moving into a new home or building, you should enquire about the age of the current ducting system to know if it needs replacing or upgrading to a modern HVAC system.

How to make ducting last longer

Making your ducting last longer is simple, but requires your attention and time. Here are some actions you can do to ensure your ducting lasts.

• Insulate your ducting.
• Repair any leaks before installing your ducting.
• Keep your ducting as short & with as few changes in direction as possible.
• If using flex ducting, ensure it is fully extended before installing, as air can get trapped in the spiral areas that are not extended, which causes dust to build up over time.

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