HVAC duct cleaning: Do you need to have your air ducts cleaned for better performance?

Air duct cleaning: a subject of diverging opinions and advice
Everyone agrees that HVAC systems need regular filter changes and clean coils. Regarding the inside of ducts, we find reputable air conditioning and heating companies who stated nearly opposite viewpoints about air duct cleaning. In addition to some licensed HVAC contractors, we found air duct cleaning services offering the cleaning the inside of air conditioning and heating ducts using a variety of methods. These include vacuuming, blowing, scrubbing, or treating with chemical compounds that are claimed to kill, seal, or prevent the growth of molds and other organisms. Often claims of better indoor air quality and respiratory health improvements are made by these services. Prices for these services vary accordingly.

The U.S. Environmental Protection Agency offers a very thorough publication on air duct cleaning. After considerable research of the literature and interviews with A/C industry experts, we can summarize this topic as follows:

Manufacturers and researchers are making steady advances in HVAC equipment and maintenance. Some of that is ongoing on flexible air ducts and duct cleaning also. Unlike regularly scheduled and essential changing of air filters or cleaning of the condenser coils outside, cleaning the inside of your air ducts should not be automatically assumed to be necessary or beneficial as regularly scheduled maintenance. There are some possible exceptions, such as homes that have vents in the floor, into which dirt and other debris would naturally fall.

Rely on the company that installed, maintains, or repairs your HVAC system
You should ask the air conditioning and heating company you trust with the maintenance (including any duct cleaning) and repair of your system what they recommend, based on what they actually observe within your air conditioning system. Why? When performing regular maintenance that is widely recommended, they already are cleaning some parts of your HVAC system and have access to the rest.

If your air conditioning and heating contractor does find the inside (dust on the outside of grillwork is normal) of your ducts or air handling system to contain significant dust, mold, etc. this indicates a problem that needs to be explored or corrected before you invest in cleaning. Why? Unless that underlying problem (such as a leaky return air duct drawing in dust, or moisture being generated or entering the system somehow) gets corrected, you will most likely have to repeat the cleaning. If the original problem appears serious enough to have your ducts replaced, you need to know this before you pay for cleaning the existing ductwork. If you are having new ducts installed, they should be sized according the ACCA publication: Manual D, “Residential Duct Design.”

Mold comes in many varieties, some more dangerous than others. If you notice the odor of mold coming from your vents or are experiencing health issues you believe are associated with your HVAC system, you should get an inspection from your air conditioning and heating company right away. If they find mold inside your system and are not replacing those components, you may wish to have it professionally tested for identification and toxicity. This could give you facts to help you decide the best course of action.

If you do elect to have your air duct system cleaned, have them clean the whole air handling system insides, not just the ducts. Why? Otherwise, the dust or mold would be spread to other locations inside the duct system instead or outside the HVAC system. After the cleaning, be sure the air ducts are not leaking from the scrubbing, air pressure, etc. The trade association that promotes standards for duct cleaners is the National Air Duct Cleaners Association (NADCA).

Generally speaking, mold growth in your home or office can be discouraged by maintaining a relative humidity range of about 30% to 50%. In many cases, your air conditioning system should do this when sized and working properly. If extra humidity control is called for, you could consider a dehumidifier or dehumdifier.

The types and functions of HVAC air ducts
Some of the most important jobs your air conditioning and heating contractor performs are the load calculations and balancing plus duct design including size and type.

Manufacturers of flexible ductwork offer a variety of materials, including metallic and non-metallic, lined and non-lined, and insulated and non-insulated varieties. If you have the need to read about standards in ductwork, you can visit the Air Diffusion Council. This organization represents North America’s manufacturers of flexible air ducts and air connectors, and produced standards for their industry titled Flexible Duct Performance & Installation Standards.

To help you understand the use ductwork, we will divide it into two functions:
supply and return.

Supply ducts deliver the freshly heated or cooled air to each zone or room. The design, size and condition of the supply ductwork determine the volume and speed of air that reaches each zone or room.

The second function of the ductwork, the return ducts, connect to the inlet side of the new system and pull air out of the inside area to be cooled or heated. One filter is located here to clean the air as it enters the system.

Have air duct leaks sealed for more comfort and lower utility bills
Whether or not you decide to have your ducts cleaned, you should definitely have your air ducts checked periodically for leaks. Leaking ducts cause up to 27 % of the losses of heating and cooling, according to the U.S. Department of Energy and other sources we reviewed. This loss causes you to enjoy less of the heating and cooling available from your system and also raises your monthly utility bills. After the short pay back period, you continue to gain more comfort and lower bills each month.