Air Talk: How Often Should HVAC Filters Be Changed (Effects)?

Residential or commercial space: When to change an HVAC filter

1. A standard home or commercial space without pets or individuals with allergies
2. For homes or commercial spaces with pets
3. Vacation homes or vacant spaces that don’t see much use: 1. Every 90 days (or 3 months)
4. Every 60 days (or 2 months)
5. Every 9-12 months (or 240-365 days)

Remember, the more your home or commercial space is used, the more frequently its air filters should be changed. It’s a simple rule of thumb that can save you from potential HVAC issues.

How an HVAC air filter works

You might wonder how we came up with those numbers. Let’s examine how an air filter works, and perhaps that will clarify any questions or curiosities you might have about air filters.

Air filters are made from spun fiberglass (the same material used in attic insulation maintenance work) or pleated paper. They are framed within cardboard for added stability.

Then, the air filter is placed in the return air duct. A return air duct is responsible for taking the air circulating in your home and/or commercial space and redistributing it, filtering it out of contaminants and pollutants.

The air duct is responsible for cleaning the air so a person can enjoy a more comfortable atmosphere with healthy indoor air. The air filter acts as a barrier for the HVAC system, preventing contaminants and pollutants from entering.

For example, an air filter blocks dust, lint, pet hair, mold, bacteria, and other delicate particulate matter.

Each air filter has a minimum efficiency reporting value (MERV). The MERV describes the type and size of pollutants that the filter blocks. In the next section, we’ll dive into the specifics of MERV values and why they’re essential for HVAC filter changes.

Exploring MERV ratings with HVAC filters

Minimum efficiency reporting values (MERV) are specific numbers that tell how well an air filter removes fine particles. You can think of MERV as a rating system for an HVAC system’s capacity to remove large and small particulate matter.

Why is MERV important, though? And what does it have to do with HVAC filter changes?

As air moves through an HVAC system, air filters trap and collect dust, dander, pollen, debris, and other small particles that can clog it. The use of air filters can provide healthier indoor air quality.

But for an air filter to do its job well, it must have the right filter, one with the proper MERV rating assigned to it.

In other words, a MERV rating tells us how effectively a filter stops contaminants and particles from passing through the filter into the air. Furthermore, filters with higher MERV ratings tend to trap smaller particles than those with lower ratings.

Breaking down MERV ratings

Here’s a quick breakdown of the number behind MERV ratings:

• Air filters with MERV ratings of 16 or below: These HVAC system-grade filters work for residential, commercial, and hospital spaces.
• Air filters with MERV ratings of 17 to 20: These HVAC system filters are used in surgical operating rooms and other contexts where cleanliness is paramount.

But, just because an air filter has a high MERV rating doesn’t always mean it’s best for your living or working space. Using a high MERV rating on a small indoor space — or a lower one on a larger one — may impair an HVAC system’s ability to filter air.

That’s because the smaller pores in highly rated air filters create resistance to airflow. If the filter is used in an HVAC system that wasn’t built to work with this resistance, the HVAC system won’t operate well.

As a result, air quality will decline, and your heating and cooling system will have to work that much more to operate at peak capacity.

To avoid breakdowns—or if you are in doubt about what MERV rating and air filter are best for you—always consult with a heating, ventilation, and air conditioning specialist. An HVAC specialist can provide tailored recommendations for air filters for your furnace or air conditioner system.

The effects of not replacing (or using) air filters

You might wonder, “What happens if I don’t change my air filter?” That’s a perfectly fair question.

Let’s start with the facts. The air conditioning and furnace filter in your HVAC system isn’t designed to purify the air you breathe as much as it is to protect your home’s (or business) HVAC system.

But that doesn’t mean that an air filter doesn’t make a difference in filtering out small, bacterial, mold, and fungi-based particles that can make breathing in living spaces more comfortable.

If you don’t change an air filter, it will fill up with dust and dirt, and your HVAC system could fail.

As dust jams moving parts—like fans, motors, and valves—less air can enter the HVAC system. Then, the HVAC system has to work harder to deliver comparable power and airflow.

Moreover, when an HVAC system becomes clogged and needs repairs, it risks damage from dust and other contaminants entering it. This can lead to costly repairs and a decrease in the lifespan of your HVAC system.

In short, your HVAC system will not perform optimally if it becomes dirty.

The best air filters to buy

When the time for HVAC maintenance comes, you’ll want to ensure you have the best of the best for air filters. The best air filter for an HVAC system is one that fits the following key criteria:

• The right size for your system (you can find this by checking your existing filter or your equipment manual)
• The right filtration level for your living space (Consider pleated air filters, as they often allow for more area to collect dust and other debris than traditional air filters)

High-efficiency particulate air (HEPA) air filters are also an excellent choice. These filters can “theoretically remove over 99.97% of dust, pollen, mold, bacteria, and airborne particles with a size of 0.3 microns (µm),” according to the U.S. Environmental Protection Agency (EPA).

With the HEPA filter market expected to grow over the next decade—especially in industrial settings—there’s never been a better time to contact a local HVAC professional for help updating retrograde air filtration systems.