Help with building foil (with image)

[reta]

I'm in full swing with the home theater room in the garage. I've put up an interior wall, insulated it, and placed construction foil in the (inner) ceiling and exterior walls (see image). However, I'm unsure if I should put construction foil in the interior wall; the space on the other side of this wall is currently neither insulated nor has any foil, so should I consider this interior wall an "exterior wall" and attach construction foil there as well?


(The home theater room is intended to maintain around room temperature with the help of a radiator and some form of Pax fan I should probably install in one of the vents)

Have I thought correctly that I should also attach the foil tightly to the timber sill instead of letting it rest on the concrete floor as seen in the image below? I will only lay a "breathable" carpet on the concrete.