Derek Cole explains that balancing dampers on each duct run let you control airflow to different rooms. Without them, you can't really adjust which rooms get more or less air. His installations include these dampers and a lifetime warranty.
Chapters
How do I balance the air being supplied to each room of my house?
Alright, that's a good question. So when we install a duct system, we actually install balancing dampers because they do need to be adjusted every now and then. So that is the route you need to take. If there is no dampers on your runs from the trunk line, then it's not really possible to do it. So that is why we install our duct systems with the lifetime warranty. By the way, we install balancing dampers with those so we can control the airflow in each room. Because sometimes you want a little more, a little less. You know, the kids blowing on turn down a little bit. My wife's okay a little more. So that way you can control the airflow. So yeah, good question. But unless you have those dampers in place, it's not really possible.