Please see attached picture. Basically I have an HVAC return duct the runs the length of the RH side of my planned theater area. I plan to construct a soffit around this hvac duct, and continue the soffit around the perimeter of the room for symetrics. The wall on the RH side of the room has to sit approximately 9.5" away from the concrete foundation wall so it will clear the furnace. The top of the wall on the RH side will sit right below the HVAC ducting with no way to really attach it to anything. It will be 9.5" away from the concrete wall so I suppose the only way to really attach it to the wall would be to attach the 2x4 spacers to the concrete wall, then use IB3 clips to attach studded wall to the spacers. Anyone else have any other suggestions?
I also have the dilemma of building the soffit around the HVAC ducting and attaching it to the ceiling as well as the wall. I plan to use IB3 clips to attach the top plate of the studded walls to the joists (where I can) and use IB1 clips with hat channel for the ceiling. Everything will be 5/8" DD with green glue. R13 in the walls and R19 in the ceilings.
One other question regarding insulation. My studded walls will be 24" OC. I had planned on using R13 for the walls but I'm having a hard time finding the 24" wide UNFACED R13. I have found the faced though. I have also found the 24" wide UNFACED R19 as well. I plan on leaving the pictured vapor barrier in place against the concrete walls. So with that in mind, should I use faced R13 or unfaced R19 in the walls?
Anyone that could offer some advice would be greatly appreciated!