MERV? HEPA? Decoding HVAC Air Filters
The hot, muggy summers and snowy winters of the Delaware and Maryland area mean your HVAC system needs to be in top form year round. Understanding HVAC air filters helps you keep your system performing well.
MERV and Filter Efficiency
MERV stands for minimum efficiency reporting value. This number tells you what percentage of contaminant particles in a certain size range the filter can trap. The higher the MERV, the more effective the filter. The number helps guide you in finding the right air filter for you.
Standard fiberglass filters have MERVs of 1 to 4 and trap, at most, 80 percent of particles 10 microns or larger. That’s enough to protect your system from debris buildup, but not enough to improve your air quality. For better air quality, look for HVAC air filters with MERVs between 5 to 11. The most efficient of these trap 95 percent of particles in the 1.0 to 3.0 micron range.
The Truth About HEPA Filters
HEPA stands for high-efficiency particulate arrestance. To legally qualify as a true HEPA filter, a filter must remove 99.97 percent of particles of 0.3 microns or larger. These filters have a MERV of at least 17. Less efficient but similar filters are sometimes marketed as “HEPA-like,” but cannot be called true HEPA filters
Because these filters are so dense, they restrict airflow in the average heating and cooling system. To avoid this problem, a technician can install a HEPA bypass system inside your HVAC system.
If you want high indoor air quality without this hassle, choose HVAC air filters with MERVs between 7 to 13. These filters, which are often pleated models, are nearly as effective as HEPA models. Filters with MERVs of 12 or higher can also interfere with airflow, so check with a technician before you install one.
At Sobieski Services, Inc., our goal is to help our customers in Delaware, Pennsylvania, Maryland and New Jersey learn more about energy and home comfort issues — especially HVAC and plumbing issues — so that they can save money and live in healthier, more comfortable homes.