Air Purifiers Vs HVAC Air Filters
Some detractors of air purifiers claim that they can get “just as good” or at least “almost as good” air filtration using a higher MERV air filter in their HVAC system. They claim that they can use a high MERV air filter instead of an air purifier to clean the air in their home.
There are many reasons why this simply isn’t true:
1. You simply cannot use a HEPA grade filter on a regular HVAC system.
The higher the MERV (Minimum Efficiency Reporting Value), the denser the filter, the higher the filter’s resistance to air flow. HEPA filters are equivalent to MERV 17. It’s physically impossible – there’s too much air flow resistance – to put this dense of a filter on a standard residential HVAC system.
In other words, you simply cannot get HEPA level filtration out of an HVAC system. You need a stand-alone appliance that is built for the specific purpose of pushing air through a dense filter. Hence, why air purifiers even exist to begin with. An air purifier is specially designed to be fitted with and process air through a HEPA filter.
Note: our testing showed that lower MERV filters (less than MERV 17) are able to lower particle concentration to a certain threshold. However, this threshold is nowhere close to the minimum particle concentration stand-alone air purifiers are able to achieve. So much so that running an HVAC system in a room that’s already had its particle concentration lowered by an air purifier will actually raise particle concentration in the room.
2. Even if you use a lower grade filter (MERV 12, for example) - lower than HEPA (MERV 17) but higher than the average filter installed in the average home (around MERV 8) - there are still major downsides that need to be accounted for.
It’s certainly possible to use an “upgraded” air filter (MERV 12, for example) that’s not quite as good as HEPA but better than what you have now (likely MERV 8 or 7) on your HVAC system but this does come with many downsides. We discuss those next.
The many downsides of using a MERV 12 filter:
It won’t filter as well as a MERV 17 equivalent HEPA filter
We just discussed this. The higher the MERV the better the filtration. MERV 17 provides better filtration than MERV 12.
It will reduce the overall efficiency at which you heat/cool your home.
MERV 12 filters are denser than MERV 8 filters. It takes more energy to move the same amount of air through a denser filter. You’re likely using your home’s HVAC system to heat or cool your home. With a denser filter the system has to work harder to move that heated or cooled air throughout the home. More power is required which results in a more expensive power bill at the end of the month.
It will put additional strain on your HVAC system.
The denser the filter the greater the strain on the system. And it’s much more costly to repair/replace HVAC parts than an air purifier.
Using a high MERV (higher than stock) filter can even damage the HVAC system.
Check your particular system’s specifications for recommended MERV. Putting a filter outside of this range on the system risks damaging it.
It has to serve the whole house which comes with its own set of downsides.
An HVAC system serves the whole house while an air purifier can be placed in a specific room. Higher MERV filters cost quite a bit more than lower MERV equivalents. They also filter the air better than lower MERV equivalents which means that they saturate with particles much sooner and therefore have to be replaced more frequently. Not to mention the fact that they have to process the air in the whole house (a lot of air with a lot of particles). All of this equates to more frequent filter replacement at a much greater cost compared to using lower MERV equivalents.
Compare this scenario to using lower MERV equivalents with air purifiers only in the rooms of your home that actually require air purification. Not only do you get better air purification (with HEPA filtration compared to MERV 12 filtration) but you also do so at a lower cost overall. The only increase in cost here is the air purifier and its filter replacements. The decrease in cost (compared to running MERV 12 filters) is substantial: lower HVAC filter replacement costs, better HVAC system efficiency (lower cost to heat/cool), lower maintenance cost, etc.
There are even downsides if you only run the HVAC system on the “FAN” setting.
You have to run the HVAC system to purify the air. What if you don’t need to heat or cool the house? Sure, you can run the system on just the “FAN” setting but this still takes much more power than using a portable air purifier.
Running just the fan on an average HVAC system can draw as much as 500 watts of power.
Top rated air purifiers draw less than 100 watts on max settings and less than 10 watts of power on energy efficient settings.
Not to mention the fact that you’re now putting additional strain on a single component of the HVAC system – the fan – since it’s on all the time instead of only automatically turning on when cooling/heating is needed.
Ducting, grilles, etc. in an HVAC system is difficult to manage and keep clean.
Air purifiers are specially designed to keep all ducting (if you can even call it that – there’s so little) and grilles clean. They’re equipped with pre-filters to minimize the rest of the appliance’s exposure to larger dust particles. They’re tightly sealed to prevent any particles from moving through the appliance without first going through all filters. Finally, all “ducting” and grilles are easy to reach and clean. The exact opposite is true for your home’s HVAC system.
All the downsides we listed above should give you pause before trying to seriously clean the air in your home with an HVAC system.
It’s our recommendation that you let your home’s HVAC system to do what it’s intended to do – heat and/or cool the air in your home.
With the average air filter (around MERV 8) installed, your home’s HVAC system will absolutely slightly clean the air while it’s heating or cooling it. However, an air purifier is the only way to go for serious air cleaning applications.
If cleaning the air in your home is a priority for you, we recommend a HEPA equipped air purifier. See here for our latest list of specific model recommendations.