236. Sealing a New Duct System
28 Jan 2026 · 3 min
Derek Cole explains North Carolina's requirement to test new duct systems for leaks using a duct blaster. Acceptable leakage is around 10%, but metal ductwork needs sealing at many joints. Aerosol-based duct sealing machines locate and seal leaks more effectively than manual mastic and tape.
Chapters
Foreign. Hey, this is Derek Cole. Welcome to the Derek Cole Podcast. Thank you so much for listening. And the majority of this podcast come from clips of videos with Q and A sessions. Sometimes I put the clip, sometimes the whole show. But usually the clips are kind of bite sized pieces so you don't, you know, have to listen to me all the time for, you know, seven, 10 minutes. But these are helpful clips and I hope you enjoy it. Again, let's get right into it.
This Star Spotlight features Derek Cole of One Hour heating and air conditioning. Today, Derek explains why it's so important to properly seal your new duct work. Derek, welcome back. Why is it so important for us to seal new ductwork? I mean, it's new ductwork. And are there regulations or specifications that are unique to North Carolina?
Anytime in this state you install a new duct system, you have to do, and Caroline knows this because she's now doing permits and do what's called a duct test or a duct blaster, as we call it. You have to measure how much leakage is in that new duct system. And there is a point, depending on the city, of the municipality as to what they want to see. 5, 10% of leakage they want. So let's go with the round number. I see it's 10, 10% leakage. So you're leaking 10% of the energy you're paying for out of that new duct system. So if you seal it, you can get down to zero, right? So if you get to zero, that's obviously more efficient than losing 10, right? So that is why you want to seal the new duct system. Now in this area, we see a lot of duct board, fiberglass duct system. Again, that is bad for your lungs, better for your health. So we go back and we install metal duct. That way you're not breathing in the fiberglass any longer. The downside to installing that metal duct is that you have joints. And no matter how much you try to seal it manually on the way there, you seal it, seal the joints on the outside with mastic, you seal it up with tape, you seal it up with insulation. You seal that up on top of the mastic and tape, still you're at 10% leakage. Because there is no way a human being can actually seal all the places that air flows. Now with duct sealing, with air seal, it works on pressure. There is not. It's an aerosol. There's not a human being, you know, putting mastic and painting it on the little joints. No, it's a machine. It's all controlled by this aerosol aerosol spray. It's working on pressure and it's filling the holes as it finds the leaks.
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