Buying Home Air Filters 101

A home air filter is easily forgotten. It does its job all alone in the basement. Day by day it’s taken for granted.

Meanwhile, it gets full of tiny particles and, after a while, stops cleaning the air so well. Time for a change, if you remember. If you don’t it’s hello allergens. Not just that, but your system has to work a lot harder to keep the house warm or cool.

A good home air filter keeps pet dander, mold spores, dust and pollen from polluting your air. Changing your filter regularly is a must to keep your air safe and ensure your HVAC system works at peak efficiency.

Here are some valuable tips to help you choose the right filter for your home.

Choose the Right Size

The first thing to know is the size of your filter. Remove the existing filter to get the dimensions. Don’t skip this step. There are too many different sizes available to play it by ear.

Most residential HVAC systems use a 1-inch thick filter. But some homes use ones up to 4 inches thick because of the volume of air circulating through the home. There are adjustable filters for non-standard ventilation openings, as well.

The air filter should fit tightly in the opening. Don’t by a thinner or smaller one because it’s easier to install. Choose the thickest one that will fit.

The thicker the filter, the better. Thicker filters capture more particles and last longer. If possible, consider having an HVAC professional modify your system to accommodate a thicker filter.

Choose the Right Air Filter Rating

Size isn’t the only reason there are many filters available at your local home improvement store. Filters are rated based on how well they do at capturing particles.

The main way filters are rated is using the minimum efficiency reporting value, or MERV. This system was developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. A higher number means more particles are filtered out.

The minimum filter rating you should use in your home is 6. Per Consumer Reports, the top performers in their tests generally have a MERV of 10, or higher.

There are other rating systems for filters, like MPR. This is 3M’s Micro-Particle Performance Rating. Filters are rated based on how well they capture airborne particles smaller than 1 micron. The highest performers have MPR’s between 1500 and 1900.

The Home Depot uses its own rating system called the Filter Performance Rating, or FPR. The scale is 1-10 – the higher the rating, the more effective the filter.

Size and rating aren’t the only criteria, though. There are many types of filters to choose from too.

Choose the Right Type

Air filters use a variety of different materials and methods to trap particles and keep them from circulating throughout your home. Below are the most common.


Inexpensive woven fiberglass filters have a single function. They block dirt and debris that could damage your furnace’s blower motor. 

They do remove some pollen and mold spores but that’s not their main job. If you consistently replace them each month and air quality isn’t a concern, they’ll work just fine.


If you want a filter that works somewhat better than fiberglass and needs replacement less often, consider a pleated one. These are also inexpensive and they need to be replaced approximately every 3 months.

The pleats create a larger surface area, up to 4 times as much as fiberglass. This allows them to catch smaller particles for a longer period of time without affecting your furnace’s airflow.


An electrostatic filter has cotton or paper fibers inside that self-charge to attract small particles. These filters are a good alternative in homes with smokers or pets. They cost more than pleated filters but are still relatively affordable.

Electrostatic filters are available in disposable and permanent styles. The permanent kind can be removed, washed and reinstalled. This allows them to last for 6-8 years.

If your home has an atypical filter size, electrostatic filters can be on the expensive side, which will add up when using the disposable ones.

High Efficiency

For folks with special situations, like allergy sufferers or those with autoimmune disorders, standard filters may not be enough.

High-efficiency filters using True HEPA technology are extremely effective at removing contaminants from your air. These filters are part of an overall air filtration system that combines a pre-filter with a HEPA filter and a charcoal filter.

The result is hospital-grade air filtration, equivalent to MERV 16, or higher. Certain systems can be easily integrated into your existing heating and cooling system.

Change Your Filter Regularly

If you remember nothing else from this article, remember to change or service your filter regularly!

The best filters can’t do their jobs right if they’re clogged with particles. Refer to the manufacturer’s recommendation for how often your filter should be changed.

Keep in mind air filters work harder in the summer months, when the air conditioning is running regularly. This happens because many blower motors run at a higher speed for air conditioning than they do for heating. Change your filter more often in the summer.

Another thing to remember is if there’s remodeling or construction going on in your home, your filter needs to be changed more often, as well. Remember, a clogged air filter doesn’t only affect air quality, it makes your furnace or air conditioner run less efficiently.

Something to know about pleated filters is clogging can cause overheating. When your unit overheats, it shuts down the burner. After this happens a few times, the limit switch will fail and the furnace won’t fire up. This results in a visit from your friendly neighborhood HVAC technician. The average cost for the part and service call is $175. Ouch!

To Sum It Up

Bet you didn’t know something you take for granted is such an important part of your HVAC system.

An air filter that balances particle filtration with unrestricted airflow allows your system to run at its best while keeping your air clean and safe. Look at all your options and choose your next air filter wisely.

Questions about air filters or your HVAC system, in general? Contact us. We’d love to help!

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