In Episode 86 of the Ask Derek Cole Show, host Derek Cole answers a caller’s questions about a musty odor in the home and a wet smell coming from ductwork. He explains that air‑conditioning removes heat by passing air over a cold coil, which creates condensation that drains into a pan. If the drain pan does not empty properly, water sits in a dark, damp spot where bacteria, mold, and other microbial growth can develop, producing the characteristic musty, damp‑sock smell. Cole recommends installing UV light (the “coil scrubber”) on the indoor coil to sterilize the surface and prevent growth, likening it to sunlight’s natural UV sterilization. When the caller asks about cleaning wet ducts, Cole stresses that the underlying problem is water intrusion—often from a moist crawl space—so merely cleaning or drying the ducts is a band‑aid. Wet insulation cannot be fully restored; the proper fix is to locate and stop the moisture source, seal the crawl space, replace any wet duct sections and insulation, and ensure a sealed duct system. He advises against superficial cleaning and emphasizes a comprehensive repair to prevent recurrence.
Chapters
Hey, on this episode we talk about why is the musty smell in my house and what do I do about the wet smell in my duct. You ask your comfort and energy questions and they get answered. This is the Ask Derrick Cole Show. Hey, this is Derrick Cole. Welcome to Episode 86 of the Ask Derrick Cole Show, answering your home and energy questions. And I don't really have anything clever to say, so let's get into the show.
Why does my home smell musty?
Musty. Your home smells musty. Yeah, musty is that kind of wet, damp, dirty socks, bottom of the hamper kind of smell. So that is musty. The reason it smells that way is because in air conditioning you have to remove moisture to get humidity out of the air. So air conditioning is all about removing heat, right? So you're taking heat out of the air, it's going over a cold coil which has refrigerant in it, and then it's coming back out cooler air than what came in. So the byproduct of that is water. So that's why you have drain lines, that's why you see water dripping outside. So what will happen is when you have that hot air going across that cold coil, you get condensation, and that's going to drip down to the drain pan. Well, if that drain pan is not draining or something is the matter, things will start growing in that drain pan because you have cold water sitting in a damp, dark spot. So the thing that happens is growth, right? So even the most— the strongest bacteria in the world lasts 24 hours. So if it's not in the air, or if it's a bug, or it's a virus, or whatever it is, it's going to die and it's going to sit at the bottom in that drain pan for a period of time. So you start getting, the first time you turn on your heat or your air conditioning, especially you get that kind of damp, musty, moldy kind of smell. There's like all kinds of molds, so we don't call it mold, we call it growth. So the way to prevent that from happening is to introduce UV into that system somehow. Now we do it here with the coil scrubber, which shines on the indoor coil has the UV power, so nothing can grow in UV. If you want to prove that point, uh, everybody at home has that mat at the front or back of the house that has the mildew and it's kind of wet and it's kind of damp. Take that mat, stick it out in the middle of the yard in the sunshine for a period of time, and that will be clean and dry because nothing can grow when UV is present, right? So In the indoor air environment, in the air handler, that is not present. So we have to make it present with UV light. UV light will solve that problem. So the same power of the sun, the same energy that holds, we can bring into your system and that will stop that damp, dusty, musty smell.
Do I need to clean my duct system to get rid of the wet smell?
This kind of goes back to the first question. We've been to some duct systems recently that have been underwater or have had water in them. So first we need to— the problem, I've seen this problem a lot in HVAC, especially in the industry, is people try to put Band-Aids on the problem and don't try to fix the problem, right? I mean, I go to the doctor, I want to be healed of the sickness. I don't want a medicine to mask over the symptoms of the sickness. Does that make sense? So I want to, I want to cure. I don't want the Band-Aid. I want to stop bleeding. I don't want to cover it up. So we need to figure out why the water is getting in the duct to start with. It's probably because the crawl space is getting moisture coming from the ground and it's getting wet that way. But once that happens, that needs to be replaced. Once you get insulation wet, There is no drying. I mean, you can try to dry it, but it's not going to be completely the way it was. So you need to go back with a new duct system, a sealed duct system, and you need to handle the problem of actually the ductwork getting wet, seal the crawl space, and then you need to replace that piece that is wet because wet insulation, first of all, stinks, and second of all, You don't know what is in the insulation. You can't completely dry it out and pretend like nothing ever happened. So I would solve the problem of getting the ductwork wet and then replace that piece. And then yes, I would seal it as well. But there is no cleaning. There is no drying out. Once you get 2 feet of water in the piece of duct, I mean, let's talk about why that's happening. Versus, you know what, my duct's rotted out, can we just clean it? We could do that and charge you for it, but let's fix the problem so we don't have this situation again. Make sense? That's it. All right, so that's episode 86 of the #AskDerekCole Show. Make sure you hashtag your questions #AskDerekCole and we will get them on the show.
