In the last picture I am moving a register (1) to (2). The left side of the picture shows where the 4" duct is sitting at the top of the wall (running across the joists). This is a bathroom. I need the duct to land at the base of that wall.
I have two options:
- use a 4 to 3 reducer and an 3 to 3 elbow and continue to use 3" all the way down to the register boot, practically reducing the size of the duct (this increases the static pressure in the AC system and will send more air to other parts of the system)
- use an elbow transition from 4" to a boot that is 10x3-1/4 and use a range duct, shown in the last picture (if this is OK)
The right side of the picture show the framing details. As far as I can see from what was done on the opposite wall (where the duct is landing now) they cut the horizontal stud and created two segments on that wall and added studs to close the two cuts (practically creating two frames joined by the bottom horizontal stud
The room size is 102x78x96=763776 cubinc in or 442 cubic feet