Can I Use a 16x20x1 Air Filter in My Furnace?

Learn how an expert HVAC technician would advise on using 16x20x1 air filters in your furnace. Find out why thicker filters are better for improving air quality.

Can I Use a 16x20x1 Air Filter in My Furnace?

The average heating, cooling, and HVAC air system uses air filters as a protective tool to prevent clean air from entering and particulate matter from coming out.


only work if air has to pass through them. The filter has air resistance and a gap does not, so if you leave a 1-inch gap, a disproportionate amount of air will flow through the hole, making the situation even worse. If your system only fits a 1- or 2-inch filter, a high MERV rating could be detrimental. A 1-inch filter with less surface space will clog up fairly quickly and will need to be replaced much sooner than a coarser filter.

Combining a thin air filter with a high MERV rate can also restrict airflow to the point of hampering efficiency and causing excessive wear. Thicker air filters tend to last longer because they have more square feet to capture and retain air particles. At the same time, a thicker filter is less restrictive and will allow better flow of purified air. A high-quality, perfectly fitting filter can keep the air cleaner and healthier, as it doesn't allow air to bypass the filter and return to indoor air. A deeper depth can also improve filter life and efficiency; it also makes it easier for air to enter and exit the filter.

Some air conditioning specialists have also found that thicker filters are better at providing a perfect fit that prevents unfiltered air from passing through. If you opt for a smaller filter or not at all, at least do something like tape or glue a piece of cardboard filling to the filter to get the correct size. The thickness of the air filter ranges from 1 to 5 inches deep. Some options are more common than others and the oven can determine the thickness that can be used. To put that into perspective, a 1-inch air filter may need to be changed every month, while a 4-inch air filter can last up to six months.

Reducing the thickness by one inch shouldn't be a big problem; for example, you should be able to use a 4-inch filter instead of a 5-inch filter. The 4-inch thick air filter has a definite advantage over the 1-inch filter in terms of longevity, airflow, and maximum filtering potential. For example, a size of 20x30x1 may appear on the filter label, but if you measure the filter, you will see that the actual size is smaller than the nominal air filter size of 20x30x1. If you try to use a 4-inch-thick air filter in a system that's made for a 1-inch-thick filter, the efficiency will actually worsen. So, if it fits your oven, a 4-inch air filter is better than a 1-inch air filter to improve air quality.

Carrie Lobato
Carrie Lobato

Friendly zombie evangelist. Infuriatingly humble tv practitioner. Award-winning web buff. Amateur travel ninja. Typical twitter fan.

Leave a Comment

All fileds with * are required