Is a 4-inch Furnace Filter Better Than a 1-inch?

When it comes to improving air quality, a 4-inch thick air filter has a clear advantage over the 1-inch filter. It offers greater longevity, better airflow, and more effective filtration potential. So, if it fits your oven, then a 4-inch air cleaner is the better option. The main difference between the two is that 4-inch filters cover a wider range of MERV ratings, with some overlap with 1-inch filters.

With a 4-inch filter, you'll get at least an 8 MERV rating, which can control supermicro contaminants such as bacteria, viruses, and dust particles. Most air filters are 1 inch thick, but some systems can accommodate filters up to 5 inches thick. In our tests, we found that the thicker the filter, the better it works and the longer the replacement intervals. This means it's better for you and your heating, ventilation and air conditioning (HVAC) system.

However, there are some cases where 1-inch and 2-inch filters may be on par when it comes to efficiency. This all depends on the MERV rating of the filter. The MERV rating is the rating that measures how well the filter blocks particles. The higher the MERV rating, the smaller the contaminants a filter can trap, which also means it will clog up faster.

Pay attention to what matters most to you and you'll discover which filter is right for you. On the other hand, a thinner filter (1) will be more restrictive and will create more air pressure on it. If your HVAC systems currently work with a filter 1, a filter 4 will not be able to fit in the existing cabinet. This means that a 1-inch filter with a high MERV rating could perform just as well as a 2-inch filter with the same rating.

All filters have a MERV rating, which marks the efficiency of the filter in removing contaminants from the air supply. We also test thicker oven filters, some up to 5 inches, and they often provide superior air cleanliness and a long service life. Now, the more CFM of air hits the furnace system, the more area it can cover with the heating or cooling action. The best air filters trap indoor pollutants such as dust, pet dander, and pollen, helping to clean the air in your home.

If you opt for a 4-inch filter, you would get a filter with at least an 8 MERV rating which would remove contaminants up to 3 microns (one unit of measure), including dust mites and some types of pollen.