Can I Use a 4-Inch Filter Instead of 1?

When it comes to air filters, the general best practice is to use the thickest possible filter for maximum efficiency. However, it's important to never try to force an air cleaner to fit in a space it's not designed for. If you try to use a 4-inch thick air filter for a system that is made for a 1-inch thick filter, the efficiency will actually be worse. The short answer? A 4-inch filter will last longer and provide better air quality for your home. Virtually any HVAC professional will tell you that thicker filters work better than common 1-inch oven filters.

Thicker filters, known as multimedia filters, are usually 4 to 5 inches thick compared to the ubiquitous 1-inch filters that can even be purchased at grocery stores. Opting for a 4-inch filter would mean that you would have a filter with at least a MERV 8 rating, which would remove contaminants down to 3 microns (a unit of measurement), including dust mites and some types of pollen. Most HVAC technicians recommend changing 1-inch air filters every 30 days, while 4-inch filters can be changed every 3 to 6 months. When you compare a 1-inch filter to a 4-inch filter, you'll see that using a thicker filter has several advantages. These media filters have much stiffer cardboard frames, and some media filters even have plastic “rails” on the top and bottom so you can slide them inside the oven with a very tight seal.

The air controller I have has a strange filter dimension that is not sold locally and I need to order it online. However, with most HVAC systems, you should be able to modernize a media filter cabinet, either under the oven or on the side. Regardless of the thickness of the filter, home and business owners should regularly inspect their filter to ensure that it is not full of contaminants. If you put several 1-inch filters together, it's similar to putting together 5 coffee filters and trying to make a cup of coffee - it just doesn't work. Thicker oven filters, known as media filters, almost always work better than cheaper one-inch filters.

These 4-inch multimedia filters can have between 20 and 30 feet of surface area with their pleated (accordion) filter material. For comparison, a 4-inch thick filter will have approximately twice as many surface areas as a 2-inch thick filter. Your HVAC technician can provide you with a new filter compartment or modify the existing one to accommodate the thicker filter. With more surface area to trap air contaminants, a 4-half air filter offers a longer lifespan than a 1-half air filter.

Ben Depauw
Ben Depauw

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