Furnace filters were initially designed to protect the furnace’s many movable parts. With time, they’ve evolved to also keep harmful particles from entering the air we breathe. And while these filters seem rather insignificant, they deserve special consideration.
There is no right filter for all people and all houses. Choosing the right furnace filter depends on a lot of things like cost, efficiency, allergies, and more. Do you need the highest level of filtration or just a basic bare bones model? That depends on a lot of questions and we’ll get some of those answers below.
Types of Furnace Filters
If you’ve been down the furnace filter aisle lately you’ll notice that the choices seem endless. So many sizes, MERV ratings (what the heck is that anyway?), disposable or reusable, electrostatic. Don’t be overwhelmed. I’ll walk you through the options here and then we’ll get into which is best for you.
Fiberglass Filters
Disposable fiberglass is the most common option but serves little purpose other than to keep large particles like lint and dust from choking your HVAC system. On the pro side, it’s very inexpensive and ideal for those who do not suffer from asthma or allergies.
The low air resistance of these simple filters means your HVAC system will operate with the least restriction which extends the life and efficiency of your system. So, if you are a bare bones, no allergy kinda person then this might be the right filter for you to save money.
Pleated Filters
Made from cotton paper or polyester, these filters are almost as popular as disposable fiberglass. They’re more ideal for people with breathing problems because they block more particles – including spores and mites. Pleated filters are also relatively inexpensive; the downside is they can tax your system by adding more resistance to airflow.
High-Efficiency Pleated
Considered the oldest of all filters, these pleated options capture many air pollutants. Hospitals use them because they screen even the smallest of particles like viruses, making them highly beneficial for those with autoimmune and/or respiratory disorders. These can be installed only in special housing units because of their thickness, and each cost around $100, making them costly but beneficial options.
Disposable Electrostatic Filters
Electrostatic filters are distinguished from their pleated counterparts in how they work; electricity is used to capture pollen, dust, and other airborne particles before they enter the air. Electrostatic filters are affordable when purchased in standard sizes and counter the effects of smokers and pets. Custom sizes, however, can be more expensive.
Reusable Electrostatic
The difference between these filters and their disposable counterparts is in longevity; the reusable variety can be removed and machine-washed for between six and eight years. Environmental-conscious users appreciate that these filters make little waste; they’re also more effective than pleated filters in capturing debris. Again, custom sizes are more expensive but may, in the long-run, save you money because they can be re-used.
Polyester Filters
Polyester provides another reusable option that traps up to 91% of common airborne pollutants, including dust and pollen. This makes them highly efficient in improving air quality. You can choose between flat and pleated options, but you still need to clean HVAC coils every few years.
HEPA Filters
Many call these the gold-standard in filters because they block almost 100% of air contaminants. The downside is availability; most do not fit standard furnaces because they come in only limited sizes. They also reduce airflow because they do block so many pollutants. For these reasons, they’re often restricted in use to hospital and commercial environments.
How Are Filters Rated?
If you’ve ever purchased a filter, you’ve likely seen its MERV rating on the outside of the package. The acronym stands for Minimum Efficiency Reporting Value. This represents a filter’s ability to capture airborne particles. The MERV scale goes from 1, lowest efficiency, to 20, highest efficiency.
The higher a filter’s MERV rating, the better it performs in trapping particles. Some of the most common particles a filter needs to capture include tobacco smoke, pet dander, carpet fibers, dust mites, and mold spores.
Higher Is Not Necessarily Better
It’s common to think a higher MERV rating is better, but this isn’t necessarily true. A higher rating means less airflow through your HVAC system, which can reduce efficiency, place damaging pressure on your system, and actually diminish your home’s air quality. The goal is to find a filter with the highest MERV rating that still permits maximum airflow. The range of ratings for the filters we discussed previously are as follow:
- Disposable fiberglass: 2-4
- Disposable pleated: 7-13
- High-efficiency pleated: 14-16
- Disposable electrostatic: 9-12
- Reusable electrostatic: 8-11
- Polyester: 7-9
- HEPA: 16-20
When to Replace Your Filter
On average, you should expect to replace your filter once every three months. This will depend on such factors as your home’s size, how often you operate your HVAC system, if you have allergies, and the type of filter you use.
A few things that will shorten the life of your furnace filter are listed below. If these are common in your home then checking your furnace filter more often would be a good idea.
- Smoking
- Regular candle burning
- Open windows
- Pets
- Kids
- Older homes
With such variables at play, it may be good practice to check your filter monthly. Also, look for dust build-up on furniture and longer heating or cooling cycles when your HVAC system runs; both can indicate your filter needs to be changed.
In the fall and spring when your HVAC system is not being used as much you may not need to change the filters as often as in the summer and winter when heating and cooling loads are higher.
If you’re a busy person like me you can use one of the services below that will set you up with automatically delivery of a new air filter in the size and rating you specify on the schedule you dictate.
These have a been a lifesaver for me any my business! I set my delivery for every 3 months at home and every month at my business since we have a much dustier environment. As soon as the filter shows up on my doorstep it’s my reminder to install it right away.
Furnace filters can significantly impact your home and your health. Choosing one that safeguards air quality and enables your HVAC system to function optimally will help you breathe better, save money, and promote HVAC longevity.
Founder & Editor-in-Chief
I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.
Scott,
So glad I read your article on furnace filters. I have always bought the most expensive $15.00 plus filters for years…..thinking I was doing the best thing for our heat and AC system. Now, that I’ve read your article, and know we don’t have any allergy problems, I will be buying the disposable fiberglass filters.
Thank you,
Nadine