Studio for audio and video on a medium budget
 

Hi. We're doing an addition to our house, and the bottom level is going to be a 22' x 16' studio for recording a show against a green-screen, and also for occasional music and vocal recording. (had considered 16 x 16, and even 20 x 16, but got the impression from varied forums that a bit longer would be much better for greenscreen work to leave proper separation between talent and screen)

Looking for any non-cost prohibitive recommendations that I should tell the builder about before construction starts. Have heard about building a wall within a wall as one of the best methods - some say to put sand between sheetrock. The studio will be on ground level poking out away from house into backyard. There will be a living area directly above it. Not planning to put any windows.

Also welcome advice on ventilation / HVAC. Thanks for any suggestions.