Weak AC Airflow – Improve Air Conditioner Air Flow

Print Friendly, PDF & Email

Find out what’ causing weak AC airflow in your home and how you can fix it to significantly improve your home’s comfort.

5 Effortless Ways to Improve Your Air Conditioner’ Operation

We’re officially entering the dog days of summer, and already we’ve seen it all: unbearable humidity, crazy freak thunderstorms and, of course, sweltering 90+ degree temperatures. It’ times like these when people everywhere are either thankful for their air conditioners or are sweating and sleeping in the basement because their air conditioners don’t work! Weak airflow is one of the most annoying air conditioner problems there is, not only because it’s uncomfortable but also because you can’t immediately be sure of what’ wrong with it. There are a number of reasons why you might be experiencing weak air conditioner airflow, some are easy fixes, some require the help of a professional.

Ways to Improve AC Airflow

Replace your filters monthly – you’ve probably heard this one so many times that it seems cliché, but it bears mentioning because it’s so important! As air passes through your home, air conditioner system and ductwork, it picks up all kinds of junk. The purpose of the filters is to catch this dust and debris so you’re not breathing it in every day.

Now, no matter how clean you keep your house, you’re always going to have dust and debris moving through your ducts, your air filters are going be catching a lot of it, and as they do, it’s all going to start slowing the airflow. This is why it’s so important to change your filters every month, if you don’t, eventually they will become so clogged that air is simply not going to be able to get through.

Changing your filters every month is important for another reason as well, if weak airflow persists in your AC, it can actually cause your air conditioner to freeze, potentially resulting in serious damage. Changing your filters is an easy way to prevent this from happening.

Make sure your AC dampers are open – if you have weak AC airflow in only one or two rooms in your home, you might not have an air conditioner problem at all, you might just have thrown off dampers. AC dampers are essentially valves in your ducts, when they are open, air moves easily. When they’re closed, either part of the way or all the way, you’ll have weak, if any, airflow from your air conditioner. To check your dampers, go into your utility room and look for your HVAC plenum (it’ll be the big, plain metal box). You should see a bunch of ducts coming out of it, all with levers that should be in the ON position, these levers are called dampers.

If any of the dampers are in the OFF position, turn them back ON, your weak AC airflow problems should go away immediately.

Change your air filters, and we’re not talking about monthly replacements this time. When you go to the hardware store you’ll see about 10 million different types of air filters, and you’re supposed to just know which is which. All of these air filters have different MERV ratings that indicate the effectiveness of the filtration. You might think more filtration from your air filters is better, after all, it means less dust in your home, right? Well with air filters, bigger is not necessarily better. In fact, if the filtration is too powerful it could block airflow!

Air filters are rated as follows:

  • MERV 1, 4: this is the standard rating for most residential air conditioners. Filters at this level do a decent job of filtering particles out of the air and can trap dust and debris as small as 10 microns.
  • MERV 5, 8: these filters are commonly used in offices or light commercial buildings, and are sometimes found in homes, especially if the homeowners want extra clean air (because of respiratory problems, etc). Filters at this rating can trap particles as small as 3 microns in size, but this filtration comes at a cost, since air has to work harder to move through the filter, homes with these filters may start to see problems related to weak AC airflow.
  • MERV 9, 12: very uncommon in residential settings, filters of this rating are usually found in much larger buildings with powerful HVAC systems. Filters that are this strong need to be replaced frequently because they will get filled up very quickly.
  • MERV 13, 16: air filters this powerful are pretty much only used in sterile environments like hospitals. Since they stop such small particles (as small as .3 microns in size) they tend to cause weak airflow with all but the strongest HVAC systems.

Seal up leaking ducts, this may surprise you, but leaking air ducts are more common than you might think, in fact, they’re among the leading causes of weak AC airflow! If you think you have leaky ducts, shine a flashlight in one of your vents and see if you can see any light coming through. If you can, call an HVAC contractor to come out and seal them up, duct sealing will improve your air conditioner airflow, making you more comfortable and saving you up to 30% on your heating and cooling bills!

Resize your ducts: if you’ve tried improving your weak AC airflow and nothing is working, the problem might be simply that your ducts are too small for the amount of air coming from your AC. Call an HVAC contractor to inspect your ducts and assess if they are the proper size, if they are not, installing new ductwork will go a long way toward improving weak AC airflow.


Editor’s Note: This excellent article was provided by Nick Massa of Magnolia Heating and Air Conditioning. Their website is www.magnoliaheatandair.com. We welcome other technicians and managers to write for our website. You will be doing the industry a favor while promting you and your company.

One thought on “Weak AC Airflow – Improve Air Conditioner Air Flow

  1. Nick says:

    Hi James

    I have an issue with airflow in my house. In my very novice opinion I feel I need more cold air returns. A year ago the previous owner installed a new Lennox HVAC unit. Its freezing cold in the basement, very comfortable on the 2nd floor, and warm upstairs during AC season. Airflow on the second floor is poor at best. I have replaced the air filter for summer flow, set the unit to circulate, installed an attic fan which helped tremendously, and I know I need more insulation in my attic. With that said I have contacted 6 different HVAC companies and none have done any calculations, two suggested installed a multi thousand dollar motor controlled ductwork dampening system to “zone out” the house. My second floor is massive, vaulted ceilings and I can only trace 4 small cold air returns. So my rule of thumb, keep it simple stupid, airflow seems to be my problem.
    I live in northwest Illinois. Can you put me in contact with a local contractor who actually cares about the science of airflow? The lennox unit is what I can determine, top of line and should be more than capable of taking care of our home. I am tired of being treated like an idiot, and given solutions that I know will not work, and trying to be sold crap I don’t need. HVAC is one of the shadiest trades in my opinion, filled with really poorly trained technicians, but I know good ones exist I just can’t find one. Please help.


Leave a Reply

Your email address will not be published. Required fields are marked *

Are You a Human? * Time limit is exhausted. Please reload CAPTCHA.