619. Air Filters | #AskDerekCole Episode 62
28 Jan 2026 · 4 min
This content was created by Derek Cole. This content was uploaded by Derek Cole. This is a podcast episode titled "619. Air Filters | #AskDerekCole Episode 62" (PODCAST) featuring Derek Cole as host in a Q&A format recorded December 30, 2024. Derek answers listener questions (an unnamed questioner) about residential HVAC and home energy topics—mainly which air filter to use, differences between filters and air cleaning, how high-MERV filters can impede airflow or be sucked into tight return grills, and why a return grill may whistle (undersized return duct/grill or overly restrictive filter). He gives practical, case-by-case advice (recommend technician assessment during annual maintenance), references building/return-sizing practices (notes a North Carolina guideline for multiple returns in larger homes), and points listeners to onehouraircarolyns.com and LinkedIn articles for more information.
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Hey, on this episode we're talking about your air filters. Which one should I have for my house? And why is my return grill whistling? You ask your comfort and energy questions and they get answered. This is the Ask Derrick Cole Show. Hey everybody, this is Derek Cole. Welcome to episode 62 of, of the Ask Derek Cole show. Answering the home energy, heating, air conditioning, air quality questions. And we have some today. So I don't know, I mean, power went out yesterday here. It was kind of. It was bad. Yeah, it was a little depressing. Yeah. But anyway, let's get into it.
What filter should I use in my house?
You should use the best filter for your home. And let me explain this, it's kind of hard to understand. It depends on your house and your duct system as to which filter you need. Now I do always recommend air cleaning, which is a different type of filtration than a filter. But if you're going to use a filter, you want it to be the right one. Now you go to the box store, they got like two rows of filters. I'm sorry, two aisles of filters. Really? Because you got the cheap one for like a dollar and then you got like the thirty, fifty dollar filters. You're like, well that one must be better because it's that much. But your system will determine what filter it can handle. So if you have a tight home, a newer home, and it's a tight construction, energy efficient construction, and your duct system is tight, then putting a really high Merv rad filter in that system could cause more problems than good. So you could put in a filter that stops up the airflow, which is a problem. On the other side of the spectrum is a cheaper filter or a cheap filter, 80 cent dollar filter you put in there and it's not very good at all because you know, only thing is stopping is sandwich bags and, and Coke cans. Anything else you throw at it. Yeah, it's 100% efficient at stopping that. But 98% of what we're trying to stop are the particles you cannot see. So if you look at your TV or your cabinet and you see dust on it, we're not trying to filter that because it's so heavy, it's sitting there. You're trying to filter the particles in the air that are coming through and those you cannot see. So you need a better filter for that. Once you get into air cleaning, then you actually stop filtration and go into air cleaning. And the reason you want to do that is because now you're getting the small particles you cannot see. And you're not stopping up your duct system. So if you go to the filter on the return grill and it's too tight and the filter is getting sucked in, then the filter is too much for that system to handle. So you need to go down in filters. I mean, it's a case by case basis. I mean, some houses are older, they're very open, the duct system is very leaky. You know, they can handle MERV15 filter in there because they're leaking so much air. Very few of that, very few, very small amounts of air are coming through there anyway. So it's not stopping it up. It's kind of a complicated answer. It really depends on what kind of system you have. The best thing to do is get the technician when he does your maintenance every year is to check your system and recommend what filter is better for you. Because some are good, some are bad. It really depends on your situation. I don't even think I answered that question. I wouldn't. Around the circles, it depends. I mean, it really does depend. I've been to a house before and his filter was too good. So I opened the filter grill and the filter is getting sucked in and the air is bypassing the filter and going through the four corners and not through the filter. So you know you're defeating the purpose of what you're trying to do, which is filter the air. So it all depends.
Why is my return grill whistling when my air is on?
It's whistling because your filter is too good. No, no, it could be that. It could be your return side duct system is too small and your filter grill is too small. Bigger is better when it comes to your return. So you really, for all purposes, in a residential application, you really can't have too much return or too big of a return grill in your house. So the return grill is too small. Therefore your return duct is too small. And therefore the air is whistling as it goes by because of a tight fit. So check your filter and probably your return duct is too small in that situation, therefore your return grill is too small. We go to a lot of homes where we go to change out a unit and the return grill is too small. It's not sized properly. Actually, in the state of North Carolina, if you have an over 1600 square foot house and you change out the duct system, you're supposed to have more than one return. So we've run that a few times and we run into the situation of the return grows is too small, so you're not returning enough air back to the system. So the system itself is sucking in air from outside, under the house, in the attic, through the walls. Whatever it has to do is getting the air to the unit. But kind of go back to the filter question. You want it to be clean conditioned air going back to the unit, and not hot, humid or cold outdoor air going back to the unit, which is not filtered. So it goes hand in hand, filter and return. Alright, that's it. That's episode 62. Hopefully answered some questions. There's quite a few. If you go to our website, onehouraircarolyns.com there are 40 LinkedIn articles you can read. Some of those are on filters as well as closing events and, you know, air cleaning. So check all those out. If you have any other Questions, hashtag them, AskDerrick Cole and we'll get them on the show.
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