Hot & Cold rooms is an issue that everyone has to deal with every day, both at home and at work. Commercial air balancing has been in place for years and is very successful if performed correctly by a certified T & B company. We have found residential to be different challenge and we have been very successful with the IAD damper system. Residential Air Balancing is different because of type of damper needed and location of damper. The challenge with manual air dampers is 1) having access to them 2) Most of them create duct leakage unless fully sealed with mastic, this then presents a problem with adjustment. Most residential air registers come with adjustable blades and some with opposed blade dampers. We have found that closing opposed blade damper does not restrict enough air and becomes very noisy. The same with closing down the directional blades, they become very noisy and lose directional air flow.
We have found that installing the Internal Air Damper in the collar at supply register will restrict the air flow needed to balance the system and allow the the supply register to remain open to obtain directional air flow as designed.  We have tested & balanced hundreds of homes and have not tested one that did not need to be balanced yet.