What Does Your HVAC Filter’s MERV Rating Mean and Which One Is Right for Your Home?

Most homeowners have found themselves, at some point, standing in front of an air filter display at their local home improvement store, staring at a variety of options, with no clue which is the right one.

How can you confidently choose which air filter is right for your home, and your heating and cooling equipment?

How can you avoid buying one that isn’t up to the job, while also skipping one that’s going to cost more than you need?

Size Isn’t Everything (But It’s Super Important in this Case)

You have to know the dimensions of your existing filter in order to shop for a new one. You can’t choose one that “looks right” or is “close enough”. It has to fit in the filter slot in your HVAC system. (Pro tip: take an old air filter with you when you’re shopping for a new one, so you at LEAST know what dimensions you’re looking for.) If you’ve accidentally bought the wrong size, don’t try to make it fit, take it back to where you bought it (they’ll almost certainly understand, as long as it hasn’t been used or jammed into a spot that’s too small for it).

MERV Ratings Explained

A Minimum Efficiency Reporting Value (MERV) rating on your air filter measures the filter’s ability to trap or block tiny particles between the sizes of .3 and 10 microns. Particles of this size are of particular concern because they can be inhaled and irritate airways — these are the particles you’re worried about having in the indoor air in your home and they include things like household dust, pet dander, pollen, etc. In short, the lower the MERV rating, the fewer of these particles the filter will trap, so the higher the rating, the more particulates will be trapped by the filter and removed from the air before it enters your HVAC system and is then blown around your house.

So you should definitely just get the highest number filter you can, right? Not exactly. Very low filter numbers (1-4) are not particularly effective at removing particulates from the air, while filters above about 13 may restrict the flow of air through your HVAC system so much that it can severely cut down on the movement of air through the system, causing a noticeable reduction in air movement, and can even possibly shut down or damage your heating and cooling equipment. Filters with a very high MERV rating may also be too thick to fit into the filter slot in your HVAC — these higher rated filters are considered “hospital grade” and might not fit into household equipment. The higher the rating, the more expensive the filter typically is, too, though the cost difference between 4 and 8 usually isn’t a lot. For most people and most homes, a filter with a rating of around 8-10 is probably best for your purposes: these will block a lot of the particulates but won’t restrict the airflow. If you have family members with high sensitivity to dust or allergens, maybe go with a rating of up to 12.

Other HVAC Air Filter Rating Systems

If you show up at your local home improvement store and you don’t see a MERV rating on any of the heating and cooling air filters, the brand you’re looking at might use a different rating system such as proprietary FPR and MPR rating systems. These products probably have an MERV equivalent listed somewhere on the box, or you can ask one of the store employees to help you find an equivalent to what you’re looking for (they probably get that question a lot, because MERV is the industry standard).

When to Talk to an HVAC Professional

Keep in mind, it’s ALWAYS ok to call your trusted, local HVAC company with questions about your heating and cooling system, and that includes questions about which filter you should be using for your HVAC. We’re happy to answer your questions — we consider ourselves your partner in keeping your family healthy and comfortable, and we want to be able to use our expertise to maximize the experience you’re having with your HVAC system and to reduce your heating and cooling stress. In particular, if you have family members with specific concerns about dust or allergies, you feel like maybe your home air filter isn’t doing its job properly, or maybe you feel like your filter might be blocking too much air moving through your heating and cooling system, definitely give us a call. Here in Cincinnati, you can call us at Jansen Heating & Cooling. We want to help take the hassle out of your HVAC experience, so you can be focused on other things.