Any air filter rated higher than 13 can restrict air flow to the point of damaging the air conditioning system, resulting in costly repairs. This reduced air flow can also affect the cooling side of the system. The cold coil inside the air controller has a preferred operating temperature based on the amount of hot air that flows through it and the refrigerant running through its copper tubing. If a high MERV filter restricts this air flow, the cold coil can eventually freeze and block air flow completely, leading to more expensive problems in the condenser coil. Most modern HVAC systems can handle higher MERV filters without issue, but if they are left unchanged for too long, they can cause premature engine wear.
A more efficient filter will be better at removing particles from the air, and won't become clogged as easily when it needs to be replaced. The new guidelines from ASHRAE, CDC and OSHA recommend updating building ventilation filtration to MERV 13 to improve indoor air quality (IAQ) and reduce exposure to SARS-CoV-2, the virus that causes COVID-19. MERV 13 filters also eliminate bacteria, tobacco smoke, vapors from cars, insecticide dust, pet dander and more. When you walk down the corridor of filters in the hardware store, you'll notice a wide selection. Knowing the potential pressure drops associated with MERV 13 filters gives you the knowledge needed to implement the controls and consider air resistance when preparing your air conditioning system for change. The MERV scale is not linear; the difference between a MERV 6 and a MERV 8 is almost double in terms of particle capture. If you're not able to use a MERV 12+ filter for your oven or air handler, you may want to look into air purifiers.
HEPA (high-efficiency particulate air) filters can remove 99.97 percent of mold, pollen, bacteria and other particles as small as 0.3 microns. Homeowners should check their air filter monthly to assess its condition and determine if a replacement is necessary. Although MERV 8 is effective in filtering contaminants such as pollen, dust mites, sawdust, mold spores and lint from the air, higher MERV ratings will further clean it. The goal of using a MERV 12 or higher filter is improved indoor air quality (IAQ): cleaner, more breathable air for everyone, especially those with allergies, asthma or COPD. This information should answer introductory questions such as “what is the MERV classification?” and “what is the best MERV rating for my oven or air handler?”.
