In the process of planning a new house. All the duct will be in the conditioned space therefore I have to plan duct chases for it (note this is not a DIY, this just pre-planning for what the contractor will need). Normal design seems to recommend that for each branch connection to a main supply duct that the diameter decrease by the capacity of the passed branch.
Is this always necessary? For simplicity if I were planning on using a lined box truss space with a constant size (assuming of course it is large enough to supply all branches off of it) wouldn't it be possible to simply balance the flow though each branch with in-duct damper?