When it comes to air filters, not all are created equal. The MERV rating system, designed by the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE), is a way to measure the effectiveness of air filters. The higher the number, the better the filter. Generally speaking, a MERV rating of between 6 and 13 is suitable for most residential homes.
This range offers a good balance between air filtration, airflow, and affordability. A MERV 5-8 filter provides good air purification in a home without affecting airflow. Meanwhile, air filters with a MERV 14 rating or higher are designed for commercial HVAC systems that can handle the coarsest filter material. If you select an air filter with a MERV 13 rating, it can last up to six months before you need to replace it.
The main difference between the MPR and MERV classification systems is that the MPR classification system focuses on the effectiveness of the filter in removing E1 microparticles from the air. Even though pleated filters have a slightly larger initial pressure drop, it's not significant enough to cause any damage to your HVAC system, as long as you change filters regularly. The best MERV rating for residential use is one that properly cleans the air in your home without slowing down airflow or straining your HVAC equipment. This means that the HVAC system must work harder to move air when using a filter with a high MERV rating.
If you don't have an old filter to calculate the measurements, you can measure the dimensions of the filter holder in your HVAC equipment. In particular, using an air cleaner with a MERV rating that is too high can damage the compressor, heat exchanger, and air conditioner coil. Since the MERV rating system is standard, it makes it a little easier to compare filters with different MERV ratings. The worst percentage of the six tests is selected as the official measure used to determine the MERV rating of a filter. Once you understand how the MERV rating table works, you can choose air filters with the MERV ratings that are right for you. Based on the above-mentioned characteristics, a MERV 8 is considered a superior filtration compared to air filters with a lower MERV rating.
The reason the pressure drop is so low for a fiberglass filter is because it is extremely porous and, as a result, ineffective at filtering. In general, if you can't see the filter media below the dust trapped in the filter, you need to change the filter. One thing to keep in mind is that a MERV 11 air filter may need to be changed a little more frequently than a MERV 8 air filter. Pleated filters that are MERV 8 to 13, unlike fiberglass, can effectively filter small particles and decrease pressure drop (this is the closest thing to MerVana you can find).