Hi, I have a new hydro-air system supplying heat to my 2nd floor. The system needs to be balanced and I had a few questions for you all.

The system is located in the attic (within the heated space) and I have an air exchanger connected to it. The system is located on one side of the house, and I have two bedrooms about 25' away, over a garage (heated to 50 deg ) that are not getting enough air and heat. The room where the thermostat is located (hallway/stairs to 1st floor) has 3 outlets.

When the system is running, there is LOTS of air coming from the 3 registers in the hall, and the area heats up quick. The 2 bedrooms do not get nearly as much air, and in fact, I questions for a while if they were connected. These 2 rooms have no attic space for a person to fit. However, I have since determined that there is some heated air coming from them.

I started shutting down the duct grilles closer to the exchanger and it seems to be forcing more air into the bedrooms. However, the closed grills now make LOTS of noise and leak quite a bit of air.

The installer is no longer around. He was employed by a GC that took all my money but never paid the subs or finished the work. So, I am short money to hire another contractor. One thing I noticed the Installer left behind were several round dampers. I have not been able to determine if he removed them from collars, or planned to install them to balance the system.

All the ductwork is flex duct, only the return is rigid. Looks like 12" trunk with 8" branches.

So, to my questions: will dampers work better to balance my system and be quieter after the install? Where do I install them and how? What is the best way to balance a new system, how would a pro do it?

TIA