You may think your biggest challenge is remembering to change your home air filter. Or maybe the size and best home air filter brand to buy once you're at the store. That's what I thought until our new heat pump started making funny noises. The HVAC technician we hired to diagnose the problem told us the problem was our air filter. He explained that the expensive “allergy” filter we'd purchased, what we thought was the best home air filter for our system, was actually preventing enough air from reaching our air handler.
The technician recommended we use the least expensive air filter available, one you can see through but I wanted to see what the manufacturer recommended, so I could show you how to find the same information for your and your HVAC systems. After several hours reviewing more than twenty websites, bits and pieces of the real story began to emerge … so here's the story every homeowner needs to understand!
This articles separates the facts from the fiction regarding home air filters. My first mistake was searching for information about air filters. They're just one component making up forced air HVAC systems that keep our homes comfortable.
Let's Start with The Facts About the Best Home Air Filter
Most houses have one or more home air filters, depending on the number of heating and/or cooling systems in the house. Any system that distributes warmed/cooled air needs an air filter for each return register, where air from inside your home is sent back to your HVAC system to be reheated or cooled again.
- Your HVAC system is designed to support your house based on the size/layout, the temperatures your home is exposed to, one/multiple pieces of HVAC equipment and the ductwork that distributes conditioned air to the rooms in your house.
- The design of the HVAC system determines the best home air filter, based on the volume of air needed to operate your system efficiently.
- Air filters insure nothing enters the return registers that could damage the HVAC equipment which will heat or cool this air.
Ideally the HVAC design for your house included a recommended MERV value for your air filter. If you don't have access to this documentation, you should ask your HVAC company when they do their annual maintenance, to give you a recommendation. They can use a manometer (measures air pressure) to determine which air filter is best, based on the size of your ductwork and the fan capacity (cubic feet per minute or CFM).
For anyone who doesn't know what type of HVAC system they have or how it operates, here is a nice overview.
Why Better Air Filters Don't Guarantee Indoor Air Quality
- Home air filters only work when your HVAC system is running, and they don't run continuously.
- Most return registers in your home are up high on the wall, or in the ceiling. The air drawn through the filters and into the ductwork aren't near the people and pets who produce what the filters want to trap, like pet hair.
- Your HVAC systems may also remain off for extended periods of time between the hottest and coldest seasons, when heating/cooling isn't needed.
- Filters that restrict air flow can cause the fan to draw air from other sources. And leaky ductwork is fairly common, drawing unwanted air from the attic, basement or crawl space where ductwork runs.
Benefits of Finding the Best Air Filter for Your Home
Remember how this story started with my my noisy HVAC system. Until researching and writing this article, I believed that using a better (higher MERV) air filter would make my home healthier, and I was the one who bought the restrictive air filter. Fortunately I asked, and listened to the technician who came to my home and now understand how using the right air filter will save me money for many years.
- Your HVAC system will run more efficiently, so your energy bills will be the lowest possible.
- When your heating/cooling system runs efficiently, it takes less time to achieve the desired temperature. That means less wear on the equipment which otherwise might require premature replacement of parts worn out due to improper operation.
- When an HVAC system runs properly, there's less chance of damage requiring costly repairs.
How to Find the Best Air Filter for Your HVAC System
I'm a homeowner like you and not an HVAC technician. My recommendations are limited to what I've learned doing research for this article on the best home air filter. We even tried to test the difference in air pressure (our home made manometer on the left) between the various air filters shown here. My preference is to pick an air filter with a MERV rating, like the FilterSnap and Ace Hardware filters we tested (3M's Filtrete filters don't have MERV ratings, making it difficult to compare them to other brands).
- Find documentation on your HVAC system design, and see if there are recommendations for the best air filter.
- At your next annual HVAC maintenance visit, ask your technician to recommend the best home air filter for your system. Listen to them with respect (they're frustrated that we don't listen to them) and ask questions until you understand the reasons behind their answer.
- Until you get an expert recommendation, buy low-cost disposable fiberglass air filters which won't damage your system. Made from spun fiberglass, low cost air filters have a MERV rating between 2 and 3, and cost between one and two dollars.
- If you need reminders to change your air filters, check out FilterSnap.com. Once you've identified the best home air filter (they offer three different MERV rated filters) for your house, you can set up automatic delivery of a new filter on the schedule you want (monthly, bi-monthly or quarterly).
- Not sure how often you should change your air filter? Look at CleanAlert's FilterScan Air Filter Monitor, which detects a drop in air pressure when your filter gets clogged and sends an alert (text or email) to your smart phone.
Our homes are becoming more complicated and it isn't always easy to find the best solution to a problem, as this article illustrates. We invite you to share your challenges and success here, so we can all learn how to be smarter homeowners.
Credits and resources for those who want to do more research:
- MillerHomeComfort.com, for their illustration of a forced air HVAC system showing the return registers, and how conditioned air is distributed via ductwork.
- HomeEnergy.org's article and chart showing the filter pressure drop by various home air filters, Is There a Downside to High-MERV Filters?
- California Energy Commissions analysis of HVAC air filters (pgs 6 to 23), as they're evaluating the feasibility of requiring certification of product performance and labeling of air filters for 3 characteristics – pressure drop, MERV and particle size/dust holding capacity.