Furnace Filter Buying Guide

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Your home furnace is a multi-tasking tool that keeps your home comfortable but also healthy and clean. From reducing dust to keeping allergies under control and helping to keep bacteria at bay, there are many benefits to maintaining your furnace. Here are some tips on how to buy a filter that works the best for you.

MERV Ratings

MERV ratings determine the efficiency of the filter and certain ratings are better suited to certain households. MERV ratings span from 1 to 20 and they measure the filters ability to capture unwanted particles in the air. The lower the number, the less efficient the filter is at trapping particles. Typically, most households will have a MERV 8-13 filter, but a filter of 15, for example, can trap even microscopic particles.


Micro-Particle Performance Ratings are designed to show you how effectively a filter can capture particles between 0.3 and 1 microns in size. Filters with the highest MPR or 1900 or higher are the most effective at filtering airborne contaminants.

Types of Filter

There are several types of filter – fiberglass is the most common and the most basic of all filters and they are made of spun fiberglass which is layered to trap larger particles like dust and debris. They can’t trap smaller particles like pollen or dander, however, so they’re usually used just to prevent dust rather than cleaning the air.

Pleated filters have double the amount of fabric compared to a fiberglass filter and typically have a higher MERV rating as they prevent more pollutants in the air. They’re a cost-effective solution that delivers high-efficiency so they’re great for people with allergies or in homes where there are pets or smokers.

Electrostatic filters use electrostatically-charged fibers which attract particles such as dust or lint as well as smoke particles, so they’re great for homes with pets or smokers as well. Finally, high-efficiency pleated filters have the highest MERV rating and these are commonly used in hospitals or areas where cleanliness is of paramount importance. They can trap even the smallest of particles and are great at preventing the spread of bacteria and germs.

Choosing the Filter Size

It may be time to order new 20x23x1 air filters, but the model and size of filters differ and will be printed on the filter itself. It’s important to match the size of the existing filter when you’re replacing the air filter, as one which is a different size is likely to be less efficient. Thicker filters can also impede airflow so it’s important to check with the manufacturer of your furnace before installing a thicker air filter to check that it will still work properly. Filters vary from one inch thick to four inches and those with a higher MERV rating are typically thicker to prevent particles passing through. It’s a good idea to check the filter at least once a month to ensure it’s not becoming clogged – if you hold it up to the light and you can’t see the light pass through, it’s a sign that it needs to be replaced.