When Should You NOT Have Your Air Duct Cleaned

ByMarc Silberberg


Last week a friend of mine, Tim, who cleans air ducts in Northern New Jersey told me an interesting story. Turns out that he had to plead with the homeowner he was called to service that he simply cannot clean this home’s air ducts. I found it kind of ironic that he would turn down a local air duct cleaning job when business was finally picking up post COVID-19. Tim explained to me that the home’s ductwork was lined with a felt-like substance that would break apart and scatter throughout the ventilation system and ultimately come back into the living area. Unfortunately, the potential customer did not understand this and was upset at him for turning down the job.

What Year Was Your Home Built In?

Before homeowners contemplate the idea of residential air duct cleaning they need to let the licensed duct cleaning professional know what year the home was built or better yet what year the ductwork was done. Ductwork done during the 1960’s and 1970’s pretty much came in the form of hard piping which is commonly found in older homes. There is no lining on this and its 24 gauge sheet metal is rolled into a pipe, making it very durable and strong. The duct was usually installed in the attic by expert tradesmen prior to putting up the sheetrock, keeping the vents free of any excess debris from the construction. However, during that period there was another type of ductwork being installed at the time, it was the flexible duct. The flexible duct is quite similar to the type we use today but instead it had a thin felt-like lining in it as opposed to the smooth vinyl lining that’s found in current flex ducts. Over the course of time the felt lining would deteriorate and begin to break up. Small little pieces would scatter throughout the duct extension and become a big problem for the heating and cooling system. At this point, the home’s ductwork should have been replaced and the last thing any homeowner wants is to loosen even more fibers from the old flex duct, potentially spreading these fibers into the conditioned space.   

The Home Does NOT Need An Air Duct Cleaning, It Needs New Ductwork

According to the company, Direct Energy ductwork should be replaced once every twenty to twenty five years. This is the best practice for a home which has the typical ductwork installed. However, if you were told by a HVAC servicemen that your flex ducts are lined with felt it’s time to have them replaced. These ducts are most likely fifty plus years old and are way beyond their lifespan. At this point the felt is more than likely to be shedding and spreading into the rest of the home’s ductwork.  

Why Should Ductwork Need To Be Replaced?

Over the course of the summer there is cool moist air that passes through the HVAC system. As seasons begin to change and the weather gets cooler, the heat is turned on and lots of dry hot air passes through the ducts. Some heating and cooling systems will have a humidifier installed in dryer climates to supply the home with some moisture so that the conditioned space should not be too dry (ever wake up with a very dry month during the winter?). The combination of moisture and heat will take a toll on the ductwork and the metal sheeting will begin to erode. Ductwork has a longer lifespan than the HVAC system but it will eventually need to be replaced. If your ducts were installed more than thirty years ago it would be wise to have an HVAC technician evaluate if they need to be replaced. Besides for the actual deterioration of the metal, the heating and cooling system’s performance will be negatively impacted. This can result in a home not cooling properly or even worse having bits and pieces of the eroding metal trunks blown back into the living areas.

What Happens When An Air Duct Cleaning Is Done For Old Ducts?

Here is where homeowners have to be smart and not think that cleaning the ducts will improve the home’s air quality. As described above, if you suspect that your flex ducts have a felt lining, the air duct cleaning equipment will only exacerbate the situation. Some duct cleaning professionals will use a soft bristle spinning brush that attaches to the head of a power drill. When the brush is activated it will loosen the debris from the air ducts. In a scenario where there is shedding felt, the brush will remove even more of the lining causing excess debris before the service man even started the cleaning. What’s even worse is when you have a non certified duct cleaner who comes in with a simple ShopVac and some tools. They officially are supposed to tape up the vents and registers and not allow any debris to escape in the house. In such a setting all of the eroding material from the old ducts will most likely escape back into the living areas which can be dangerous to anyone especially those with compromised respiratory systems like seniors and children.

Using a Reputable NADCA Certified Air Duct Cleaning Company

Before any duct cleaning is done it’s important that a thorough inspection of the ductwork and HVAC system is done. The serviceman should be able to identify if any harm will be done to the home’s ductwork during the duct cleaning process. You might even be surprised to hear that your ducts don’t need to be cleaned at all. There are certain signs to look for before requesting an estimate from a reliable duct cleaning company, like dust around the grills and registers. Sometimes you may notice mold around the bathroom fan that could signal that there might be mold present in your ducts. There should be a specific reason as to why you’re requesting the duct cleaning in the first place. Always be on the lookout for possible duct cleaning scams. The general rule of thumb when it comes to air duct cleaning is that if the price looks too good it’s most likely a scam. 

Fiberglass Flex Duct Cleaning 

Before going into whether or not fiberglass flex ducts should be cleaned, let’s first get a bit of understanding about it. This type of duct consists of a metalized polyester jacket reinforced with fiberglass scrim. The idea behind the fiberglass flex duct is to provide extra installation for keeping the air warm until it reaches the conditioned areas. Sometimes a duct might run through an attic or crawl space that gets really cool during the winter time and may have an impact on the warm air running through the ducts. The fiberglass insulation will keep the air which passed through nice and hot for ultimate warmth during those cold frigid winter days.

The problem is when the fiberglass flex duct needs to be cleaned. First of all not always is the pipe to be cleaned accessible and second of all, it is lined with fiberglass which can be become loose when a cleaning is attempted. If there is mold present in the fiberglass flex duct it will be impossible to clean and that’s why the only solution is to replace it. There are certain things that even the best mold removal companies can’t disinfect and a fiberglass flex duct is one of them.

Final Words

There are many things in this world that can be of benefit to us while at the same time hurt others. For example, filling up a truck with diesel gas will allow the engine to run smoothly while filling up a passenger vehicle with such fuel will only damage it. The same is true for HVAC air duct cleaning. When the service is performed in the proper setting it will clean the home’s air ducts and improve conditioned air quality. At the same time, homeowners can see a reduction in electricity bills as the heating and cooling system will tend to perform better. However, if the system is sensitive due to its age or type of ductwork, the duct cleaning will make things worse. The last thing you want to have is for you to worsen a situation and cause the ducts to become even dirtier. That’s why it’s vital that you get an in-home estimate from a local reputable duct cleaning company that will be honest with you on whether or not they can service your home. There does come a point in time in a home’s lifetime that the ductwork will need to be replaced. Once the new ductwork is installed you should see your HVAC system performing better. 

If you are purchasing an existing home, make sure the engineer not only tests the heating and cooling system but inspects the ductwork as well. Existing home buyers will focus on if the system is working properly and tend to not even think of having the ductwork inspected. Make sure to ask the engineer if they can inspect the ductwork to look out for signs of leaks or erosion. Having to replace the ductwork is expensive and that’s the last thing an existing home buyer should have to deal with.   

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