Derek Cole explains HVAC filter ratings: higher MERV numbers trap smaller particles but restrict airflow, while too-high ratings can choke your system. He recommends MERV 8 as the sweet spot for most homes, and shares a salt test to check if a filter actually works.
Always a very good question because these days you're going down the aisles of Walmart or Home Depot or Lowe's and you see all these filters in the aisles. You're like, there's a lot of choices on filters. What does it mean? What should I do? It's also one of those situations— well, well, I mean, the, the answer is it depends. Unfortunately, the answer is it depends. It depends on your duct system and what kind of filter it can handle. Filters are rated by what we call— well, not we, what it's called— a MERV rating. Basically, the higher the number, the more efficient the filter is at collecting smaller particles. So obviously a MERV 6 isn't as good as a MERV 13, right? See what I'm saying? But the sacrifice with these, with increased filtration with the higher number MERV rating, the sacrifice is airflow. That's always the balance and the challenge you're going to get into is, yes, I want to get the particles, but I also want to have airflow. My system needs to breathe. My system cannot breathe if, if the filter is too good, too high of a MERV rated filter. For my system. Um, you know, I'm trying to go with a MERV 13, and you know, every time I put it in, the unit comes on, I look back at my filter and it's sucking it in, it's like caving it. That's not good either. So there's always a give and take with airflow and with trying to get the particles. What we provide here for our club members is what's called a MERV 8 filter. To me, it's a good middle, middle of the road, you know, not too, uh, not too tight as to mess up a duct system, but also not so poor that it lets just anything fly through the filter. It kind of, you know, it's kind of middle of the road, um, but it's what we provide our club members. Of course, you can use something different than that, but it's a— there's a— you got to watch that. There's always a give and take. You know, if you have a sealed duct system, obviously you don't want a, uh, you know, the highest MERV rating filter ever because you're gonna have an airflow challenge. If you have a poor duct system and it's not sealed and you go with the higher MERV-rated filter, it's going to, you know, not suck it in, not be so tight. But the problem is it's a poor duct system. So air is coming through the filter, air is coming in the crawl space, from the crawl space, from the house, from the attic. You know, it's coming from every direction, whereas you want the airflow to come through that filter so you can control what's getting back to unit. And you want to be clean, crisp air coming back to the unit, not dirty cross-bake— cross-space, attic, um, house, outside, uh, all this kind of air that is not filtered before it gets to the unit. You don't want want that challenge. So that's why I say there's, there's always a give and take, uh, between which, which one you can go with, uh. But when the technician comes to your home, they can definitely look at it and see which one's the best fit for you. But, um, which air filter? It's a good question. There's a lot of options. Um, typically I've seen the extremes. I've seen folks go with the air filter that's too much for the unit. Uh, it's too, uh, it's too hot. It's an allergy-rated MERV, you know, 13 filter. Well, every time the unit comes on, that the filter is getting sucked into the return, and it's not helping because it's getting sucked in, and the air that you're trying to filter is going through the four corners because it's being sucked in. So that's a challenge. And then the— on the other spectrum are the folks that, you know, get the basics, uh, you know, the $1 or 80-cent filter at Walmart or Home Depot, and it's too loose. It lets too much fuzz through. It doesn't filter anything. I've always said a good rule of thumb is you know, to lay that filter on the counter, pour salt over the filter, and see— and pick up the filter and see if salt made it through the filter. Uh, if it didn't, let's go with it. If it did, it's not good. You, you don't want to put that in your system. So again, always a give and take, but, uh, here, uh, we provide a Mervate-plated in the middle of the road, not too strong, not too light kind of a filter. And I believe that's a good, a good middle of the road.
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