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Do You Know What MERV Ratings to Look for When Replacing Your HVAC Air Filter?

The air filters on your heating and cooling systems play a critical role in keeping dust and debris out of the ducts and HVAC equipment. They also improve your home's indoor air quality. Selecting the right air filter is not difficult when you know what to look for. It starts with understanding MERV.

Most air filters sold in the United States show a MERV rating on the packaging. MERV, or Minimum Efficiency Reporting Value, is a scale that runs from 1 to 16 for residential filters (with HEPA filters running MERV 17-20). The scale rates how well a filter removes fine particulates from the air. The higher the MERV rating, the smaller (and more) particles the filter will remove.

Types of particles a filter can remove at different MERV ratings:

  • MERV 3 – Whole dust mites and some pollen (minimal residential)
  • MERV 7 – Mold spores and hair spray (better residential)
  • MERV 12 – Legionella and Lead dust (superior residential)
  • MERV 16 – Bacteria and most tobacco smoke (hospital)

Now, before you go out and buy a MERV 16 filter for your HVAC system, you need to consider how much air will get through the filter. For air to move through a MERV 13-16 filter, you need an air handler or furnace blower that can put out a great deal of pressure. Most homes cannot produce that much pressure, without being extremely inefficient or causing damage to the equipment. Plus, these filters are usually much wider than standard one-inch-thick filters, so they'll need special installation in your HVAC system.

How Do You Select the Best Air Filter for Your Home?

Most home air filters fall into four categories: fiberglass, pleated, electrostatic and high-efficiency pleated. Each has its own advantages and drawbacks:

  • Fiberglass panels are probably the most familiar kind of air filter. Relatively low cost and easy to find, this kind of filter offers the lowest level of filtration. Most of these filters have MERV ratings of 2 or 3. These filters are great for renters or for those who do not have to filter out indoor allergens.
  • Disposable pleated filters are a step up from the basic fiberglass panel. A cotton or polyester pleated panel provides the filtration element. The pleating offers a greater surface on which to catch particulates. These filters can range from 4 to 8 on the MERV scale and are slightly more expensive than a fiberglass panel. Its biggest drawback is the amount of air resistance this filter offers. Filters with higher levels of air resistance can drive up the energy costs of your HVAC system. It's important to inspect the filter regularly and change it when it looks dirty.
  • Electrostatic filters contain self-charging electrostatic fibers that attract particles and trap them. They are generally more effective than pleated filters and do not have the problem with air resistance. Disposable electrostatic filters are more expensive than the disposable pleated filter, especially in non-standard sizes. The permanent filter has a removable, machine washable panel that can be used for up to eight years without replacement. MERV ratings on this kind of filter range from 8 to 10.
  • A high-efficiency pleated filter can be 4 to 5 inches deep and must be specially installed into the ductwork near the air handler or furnace blower. The filter contains deep pleats within a rigid frame that prevents leaks and fluttering. This kind of filter may be seen in hospitals or the homes of people with auto-immune disorders. The filters can last up to a year, but have MERV ratings up to 16, which is near HEPA filtration level. These filters are the most expensive and do require modifications to your home's ductwork.

No matter what kind of filter you choose, be sure to change the filters as often as recommended. Even the most efficient filters will become clogged with time. A clogged filter does nothing for your indoor air quality and reduces your HVAC's efficiency. It can also cause damage to your equipment.

You can talk to an HVAC professional to learn more about air filters and MERV ratings. If you need an HVAC contractor in Chicago, northwest Indiana, or southwest Michigan, let us help you. Comfort24-7 can help you find a local contractor today.

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