I'm building a 15 x 26 addition off of current family room to use as a music room. The family room has 2 vents(registers) where the family room meets the new room, and because of convenience they extended the 2 into the new room. That's fine cause they were lined up perfect.
The issue is they were told to replace what they stole from one room, and now want to split that duct run from the one register to two. Basically they want go up to feed original duct, then keep going and feed new room.
My concern is the family room will not be getting all the conditioned air that it originally did, and will be too warm in the summer and too cold in the winter because of the reduced flow. they robbed Peter to pay Paul so to speak. Am I crazy for asking for replacement runs with registers to original family room?