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Air Filter Guide: What You Need to Know About MERV Ratings

Posted by Kelly on Oct 21, 2015 4:26:29 PM

merv_rating

Being at the hardware store, walking down the HVAC aisle, and looking through filters for your home’s furnace probably doesn’t sound like a fun way to spend your free time. But we’re here to tell you, with a little knowledge and know-how, you can be an air filter expert and spend more time doing what you love instead of worrying about how to keep your furnace running. (Hint: Changing your filter frequently is one of the best ways to achieve this!) One of the first steps to being a filter expert is to understand MERV ratings – or how a filter is ranked for efficiency. Knowing about MERV ratings can help you walk in and out the next time you need to run to the hardware store for a filter. So, let’s get learning!

What Is A MERV Rating?

The HVAC industry ranks air filters based on effectiveness. That ranking is called MERV, and stands for Minimum Efficiency Reporting Value. It helps homeowners and technicians compare air filters to find the right one for both their needs and the HVAC system. Basically, filters with higher MERV ratings provide better filtration and are more expensive, because they are more efficient at getting particles out of your indoor air. They are usually thicker, too. Filters with lower ratings are typically thinner and less expensive, because they don’t collect as much dirt, debris and allergens from your air.

What Does MERV Mean To Me?

It may seem like a no-brainer just to get a better-ranked filter when you are at the store, but it’s not quite that simple, according to our resident expert, Keith Hill, technical support manager at Minnesota Air. 

“A higher efficiency filter almost always means more strain on the system. That’s not to say that your system can’t handle it – that’s the unknown,” he says. “It takes more horsepower to push air through a higher efficiency filter (because there is a) higher energy draw for the furnace motor. Also, there is usually a reduction in airflow with a high efficiency filter.”

A little less airflow may not be an issue, but if airflow decreases a lot, it will cause trouble and overheating, and could possibly shorten the lifespan of your equipment.

It’s always best to use the same filter that your system was set up with when it was installed and checked out by the installing contractor. However, if you would like to try something more efficient, that’s great, just ask a pro to verify that it will work in your system, says Keith.

Are The Less Expensive, Lower-Rated Filters OK To Use?

Yes! You don’t need to spend money on a higher rated filter unless you know you have people in your home with allergies or medical issues.

A typical household would do just fine with a filter with a MERV rating of 6 or 8. For those households that have people with allergies, choose a MERV of 8 or 10. A filter with that rating will remove smaller dust and pollen particles.

Just make sure the filter is the right size regardless of MERV rating.

“If it fits, it must be okay to use in my system – is not always true,” says Keith. “Pleated media one-inch thick filters are really more for commercial use, but we see them used more and more in residential. Pleated filter media looks like “accordion” folded paper. They are more efficient than fiberglass or mesh filters, but also more restrictive to airflow.”

And most importantly, change your filter often. BobVila.com says to do it at least every three months, but in months of high use – or if you are doing work inside your home (drywall, painting, construction) – even more.

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