It’s very common for commercial buildings to have filters of the wrong size installed in their HVAC systems. When Joe W. Fly Co. technicians perform inspections, we see filters that do not fit properly on nearly 100% of our surveys. It is common to see these things on all types of buildings in all industries. And many times, the owner or maintenance manager is not aware there is anything wrong.


Joe W. Fly Co. President Trey Fly explains why building owners and maintenance managers are often unaware of problems with wrong-size filters.

Why Wrong-Size Filters Are So Common in Commercial Buildings

Building engineers or maintenance workers end up using incorrectly sized filters for a variety of reasons. When a new engineer arrives at a building, the norm is to continue using the filters that have been used in the past. When a commercial building is sold, the new owner often inherits these problems.

It’s possible that at some point, a building’s current engineer didn’t have the right size or quantity of filters on hand and was forced to rely on stop-gap measures, such as gaskets and spacers, to block air from bypassing the filters. But these short-term solutions cannot fully alleviate the negative effects of air bypass.

How Air Bypass Increases Costs and Reduces Air Quality

You might have a unit intended to be filled with 5 to 10 filters. Air follows the path of least resistance, so even seemingly-tiny gaps between these filters can let through enough unfiltered air to effectively decrease the MERV level of your filtration system.

When the air in an HVAC system bypasses the filters, the unfiltered air can be harmful to the health of building occupants and the success of critical business processes. This situation can be detrimental in any industry, but it can be severe—even costing millions of dollars in lost product—in highly regulated industries such as pharmaceuticals or semiconductor manufacturing. Expensive lawsuits are also possible if air isn’t properly filtered in health care facilities.

In addition to poor indoor air quality, air bypass can contribute to equipment breakdowns and decreased system efficiency. Coils can become dirty, causing the compressor to work harder to push air through—increasing energy use and costs.

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How to Fix the Problem and Optimize Your HVAC Filters

The only true solution to eliminate air bypass issues is to ensure that the right quantity, size, and efficiency filters are installed—and that they fit properly. Gaskets can be added to the track or holding frame to improve the seal, but it is recommended to avoid using spacers. They often don’t fit perfectly, leaving gaps. Even worse, many times when spacers are removed to change the filter, they are never put back—allowing the problem to become even worse.

Joe W. Fly Co. does more than sell air filters. Our technicians conduct thorough inspections and offer recommendations based on our many years of experience in the filtration market. In many facilities, it’s possible to generate substantial savings by ensuring that the correct sizes and types of filters are used consistently.

Another solution that helps reduce costs is to install a custom metal filter frame in place of the disposable filters used in most facilities. This frame covers the entire filter track and is guaranteed to eliminate air bypass. By ensuring that all of the air passing through your HVAC system is properly filtered, you’ll minimize labor and energy costs, and avoid the burden of having to clean your HVAC coils frequently.

Contact Joe W. Fly Co. today to learn more.

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