Hey Ed, What’s the difference between 100 CFM coming out of a metal duct or a flex duct?

In this edition of “Hey Ed,” Ed discusses the difference between a metal duct and a flex duct when 100 CFM is going through it.

Hey Ed, what’s the difference between a 100 CFM coming out of a metal duct or a flex duct? This is one of my favorite discussions to get into with folks because the difference is not a. Whether I’m getting a 100 CFM out of a flex or a metal duct is irrelevant. There are far too many people out there that are concerned with the material because they don’t measure stuff. And they just assume that one product is better than the other. At least when it comes to airflow, it does not matter as long as the person that’s doing the sizing does a proper job. Now, one material might do better when it’s done improperly, but I’m going to completely ignore the whole done improperly thing. Simply for the fact that 100 CFM coming out of the intentional hole in the duct system is 100 CFM. And that’s the way I see it.