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Five Common Causes of Low Airflow in a Home

At National Heating and Air Conditioning, we frequently receive complaints about room-to-room airflow in homes. Cincinnati homeowners often associate the comfort of a room with airflow.

There are many reasons why airflow can be low. In some cases, it may just seem like the airflow in a room is low, causing the room to feel uncomfortable, but testing proves that’s not the case.

As discussed in the article titled “The Two Primary Causes of Reduced Airflow in Ductwork” on the Energy Vanguard blog by Dr. Allison Bailes, the two main causes of reduced airflow are friction and turbulence. Below, we’ll look at a few of the most common issues that cause friction and turbulence in HVAC systems.

1. Dirty Furnace Filters or Excessively Efficient Furnace Filters

This is an example of friction. The thickness of the furnace filter should be taken into account when the ductwork is designed and the fan speed is set. If the thickness is increased because the filter is dirty, it changes the pressure of the moving air, restricting it and causing uneven or inadequate air distribution.

In today’s world, indoor air quality is a highly-discussed topic. Furnace filters are a large part of this conversation. They come with MERV ratings. MERV stands for Minimum Efficiency Reporting Value.

MERV ratings range from 1 to 16. The higher the MERV rating on a filter, the fewer dust particles and other contaminants can pass through it. The MERV scale represents a filter’s worst possible performance at removing particles 0.3 to 10 microns in size (really small stuff!).

Some of the common particles that filters are tested for include:

  • Pollen
  • Dust mites
  • Textile and carpet fibers
  • Mold spores
  • Dust
  • Pet dander
  • Bacteria
  • Tobacco smoke

Most residential systems can adequately remove airborne contaminants with a filter rated MERV 7 to 12. The higher the MERV rating, the smaller the pores are for air to flow through your furnace filter. Smaller pores can create more resistance in airflow than a system is designed to manage, thus making it inefficient. That reduction in airflow can then cause the very problems the filter is meant to solve. It can make indoor air quality worse and put a damaging amount of pressure on the fan of your furnace or AC system.

So, if you’re experiencing furnace airflow problems or you’re wondering why your furnace is not blowing hard enough, make sure your system’s motor is rated to handle high MERV filters.

If it isn’t, you’ll need to change the filter regularly (more so than with a normal filter) because of airflow restrictions.

2. Crushed, Blocked, Improperly Installed or Disconnected Duct Runs

This one may seem like a no brainer, but we see it all the time. Each duct run in a home should be designed and installed to deliver a certain amount of air to a certain space. Anything that changes the configuration of that ductwork also changes its ability to deliver the correct amount of air.

If the ductwork is installed in a manner that restricts the airflow, then the area may never get the air it was designed to get. The longer the air has to travel and the more turns and bends it has to travel through, the more turbulence is created and the less likely it is to make it where it is intended to go. Throw in a crushed or partially crushed run, bent, or kinked piece of flex, and you’re not likely to get the air you’re supposed to.

Wondering how to increase airflow to one room in your home? Are you dealing with no heat coming out of vents in one room? Contact us for an HVAC system inspection!

We serve all areas near Cincinnati, OH, including Forest Park, Hamilton, Loveland, Mason, and more!

3. Duct Leakage (Including Home Leakage)

Over 90% of homes in North America have air duct systems that contain small holes and cracks. These reduce the level of comfort and increase heating and cooling costs.

The Department of Energy tells us the typical duct system has between 35-50% leakage. This means 35 to 50% of the air meant to travel from the air handler to a certain area of the home is not making it to its intended location.

In the world of residential energy efficiency, if the ductwork isn’t in an attic or crawlspace where there are large energy penalties suffered because of leakage, it is often ignored. The common reason for this is that if the air is leaking inside the home, it isn’t that big of a deal because it is still inside the conditioned area and still, in effect, heating or cooling the home. This line of reasoning only makes sense if you are only worried about the energy lost, and not the comfort of the rooms you are trying to heat and cool.

That’s not to say leakage outside the conditioned area doesn’t affect comfort. It most certainly does-in a big way! But air not getting to the intended rooms also affects comfort, whether it leaks inside the home or not. Sealing a system from the inside out using a process known as Aeroseal can increase airflow up to 50%!

Once all the air that the air handler is trying to produce is accounted for, it is important to balance the duct system to make sure each room is getting the intended amount of air. As Dave Richardson of the National Comfort Institute (NCI) discusses in his blog article “The Building Side of the Duct System,” air leakage and insulation levels of the home can play as big a part of poor airflow as the ductwork itself.

Experiencing poor airflow from your Cincinnati home’s heating or cooling system? Give us a call today at (513) 621-4620 or contact us online now!

4. Not Enough Return Air Vents

A typical forced air HVAC system is designed to a closed loop system. In a perfect world, it produces a certain amount of air, and that air is distributed throughout the home so the same amount of air is returned from the home, conditioned, and then redistributed.

Each area that is receiving a measured amount of air should also be able to return the same amount of air to the system. If the return is not sufficient:

  • The area becomes pressurized.
  • The amount of airflow it can receive is limited.

It is a similar concept to blowing into a straw: As long as both ends are open you can blow as much air as the size of straw allows for. But as soon as you restrict one end, the amount of air that can pass through the straw becomes limited. Close one end all the way and the amount of air you can blow in becomes finite!

Are you experiencing uneven heating and cooling in your home? Call National Heating and Air Conditioning today at (513) 621-4620 to learn more about our HVAC services in Cincinnati, Ohio!

5. Undersized Vents or Oversized Ductwork

Air moves through the ductwork and to its intended location by maintaining the correct static pressure. If the ductwork is too big, the pressure of the air will drop, never reaching its intended destination.

More often though, the ductwork is too small. This will cause restriction to the point that the measured amount of airflow is not reaching its intended destination.

Ready for help getting your airflow back on track in your Cincinnati home? Contact National Heating and Air Conditioning now!

Fix Low Airflow Issues with National Heating and Air Conditioning

From blocked or leaky ducts to clogged filters and dirty coils, if you have a problem with your heating and cooling system, you can rely on our experienced HVAC contractors to get to the bottom of your issues and offer affordable, reliable results.

At National Heating and Air Conditioning, we understand that low airflow is commonly a result of one or more issues needing HVAC repair or maintenance. With a professional heating and cooling inspection, our technicians are able to:

  • Perform the proper inspections and diagnostic tests
  • Assess what is causing low airflow in your home
  • Provide you with options you can count on to improve the overall airflow in your home

Suffering from poor airflow in your home?

If you live in Greater Cincinnati, Northern Kentucky, or Southwest Indiana, Forest Park, call us today at (513) 621-4620 for reliable airflow and HVAC services!


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