It’s not often that air ducts need to be replaced unless for some reason they were damaged or altered in an incorrect way that effects the efficiency. I do recommend cleaning the air ducts every three to five years. While the EPA has conducted several studies to reach their recommendations, other governmental bodies are also participating in studies to determine the effectiveness of cleaning vents and air ducts. Duct cleaning is beneficial for reducing the amount of dust on the surface of return-air ducts only and not necessarily supply-air ducts. Cleaning air ducts results in lower concentration of microorganisms such as mold and bacteria. Best practice involves cleaning the return-air ducts only and the air handler/furnace to boost air circulation. Some recommendations as to when you should clean your air ducts are:
When you move into a new home.
After building a new home.
After completing a home remodeling project. Construction projects spread sawdust throughout the home, and unless you go the length and protect the ducts, the dust will extend into the ductwork, too.
If some home occupants have severe allergies.
If you have many pets in the home that shed fur or dander.
You can also get more reference information from the National Air Duct Cleaners Association (NADCA), the only organization that exists to serve the duct cleaning industry and protect consumers from fraudulent contractors.
Hope this helps.
If your air ducts are dirty, this is due to infiltration. A duct system is intended to be a closed-loop. The 2006 International Energy Code requires duct systems to be sealed with mastic, but this was not always the case. If your duct system was installed more than 10 years ago, I can almost guarantee it is not properly sealed. It may have been sealed with duct tape, which will deteriorate over time; or it may not be sealed at all. This leads to decreased efficiency and performance of equipment, as well as increased energy bills and infiltration of dust and attic / crawlspace / basement air into your duct system, and eventually your home!
Also, all ducts located in an unconditioned space, such as a crawlspace or attic, should have 3" / R8 insulation.
If your duct system is not sealed with mastic sealant, I would recommend at least having every accessible connection properly sealed. In some cases, it is better to replace the duct system with a properly designed, 100% mastic-sealed duct system. Sealing your duct system is more important than having your duct system cleaned! I would recommend sealing the duct system, THEN having the ducts cleaned, if they are dirty. Otherwise, you will be having them cleaned every few years.
The EPA need not be brought up as if they are some kind of authoritarian body on the subject (which they are not).
Your air ducts should not need to be replaced, unless they are damaged in any way, by whatever means that they can no longer be re-sealed, repaired, or re-insulated.
As far as cleaning air ducts is concerned, it is difficult to properly clean air ducts in any given system, due to air duct dampers impeding access, and other situations causing restrictions to air duct access, but it can be done.
Jim at All Temp Refrigeration, Inc. Santa Clara, CA.
Air distribution systems are an independent system from the heating and air conditioning system, both must be compatible for optimal performance. Heat and air equipment today require larger ducts to move the required volume of air to prevent unsafe operating conditions to the equipment. My experience has found return air duct and filter grille area have been undersized on 75% of new systems requirements. This undersizing creates a noisy air system at the return. Flexible air ducts life expectance is around 20 years, if outer vapor barrier is damaged time to replace. Fiberglass duct board life expectance also 20 years, if water damage time to replace. Sheetmetal duct seal and verify insulation integrity is good practice.
A duct system more than 15/20 years old is likely undersized for the technology of today.
Redesigning the duct system may be necessary on new system change outs. Good contractors will inform you of needed changes to meet the new system. Cost burden are the stumbling block here for most home owners.
There are many conditions that demand replacement of air duct. If you want to improve overall performance of your HVAC system, you have to do periodic cleaning and system checking. The major conditions that compel us to change the complete system are if your HVAC is more than 10 years old, if you didn’t find your home heating or cooling properly, if your system have leaky ducts and many other. http://ventilationreview.com.au/
The only true reason you should ever have to replace your duct work are as follows:
-Damage to the duct system that adversely effects performance of the system, including rust, holes, dents, etc. Most small things can be repaired.
-Undersized or over-sized when they were first installed or the home has been upgraded and is now more energy efficient, requiring less Heating or cooling, and therefore the system will not match the duct work.
-Additions have been added and you want the same system to take care of it (not recommended to use the same system usually. Adding a 2nd system or mini-split is usually favorable)
The Truth is, if it was done properly, the duct work could last as long as the home. As is the case in many homes, however, the duct work will be incorrectly sized and need modified in some way to suit newer equipment, and sometimes, this modification can result in it making logical sense to replace it all.
