Ross and Witmer 
The two-pronged purpose of effective HVAC air filters is to protect your heating and cooling equipment and your home’s air quality. There are many types to choose from, however, and it can seem a difficult decision unless you understand the differences in ratings, materials and designs. Here is a brief guide to help you choose when shopping for air filters.
Efficiency Ratings
The efficiency of an air filter indicates the size of airborne particulates that it’s capable of trapping. The standard rating system is MERV, or Minimum Efficiency Reporting Value, and the range runs from 1 to 20. HEPA filters, which are the highest efficiency air filters, are rated between 17 and 20.
Not all retailers carry MERV-labeled filters, however. Sometimes you will encounter other rating systems, usually tied to a manufacturer or store chain. In these cases, you may need to contact the manufacturer if you want to know the MERV equivalent of the alternate rating system.
For better air quality, it’s always best to choose medium- to high-efficiency filters. However, this does not mean you need to purchase the highest MERV or HEPA filters – in fact, your system may not be compatible with these due to airflow resistance. Consider choosing instead a filter with a MERV rating of between 7 and 12 for a good combination of air cleaning and airflow maintenance. If you choose a high-effiency or MERV filter, your HVAC system likely will require physical modifications to work with that filter.
Size
If you’re not sure what size filter to purchase, the easiest way to find out is to look at the existing filter in your forced-air heating or cooling system. The size should be marked on the filter’s side, or you can measure it yourself.
Materials and designs
- Fiberglass filters are inexpensive and relatively inefficient. They will help keep some dust out of your HVAC system but will do little for your air quality.
- Polyester filters are more efficient at catching particles and are preferable over fiberglass.
- Pleated filters have a greater surface area, which helps them trap more particles.
- Washable filters are convenient but not efficient. While fine for window air conditioners, avoid choosing these as your primary HVAC filters.
- Electrostatic filters attract and hold onto dust and other particles due to the filter’s electrostatic charge.
For more information about air filters and your HVAC system, please contact us at Ross & Witmer. We provide exceptional services to Charlotte and the surrounding area.