Garage soundproofing - planning

[Jazz Monkey Jr]

I am planning to turn my garage in to a cinema room, I am starting from scratch although the ceiling is already plasterboarded/plastered due to the extension above it.
I want it well soundproofed, I am going to go for the stud/rockwool, soundbloc/green glue/soundbloc way nn the walls/ceiling. I will probably rip the old ceiling down to get cables in.

I have a small window at one side (the outside wall), I am going to brick up the front and put a window in, see pic. The other side wall is joined to the house therefore is a cavity.

My question is: How much sound will I loose out of the windows? I was thinking about putting an extra layer of greenglue/soundbloc but there isn't much point if loads of sound is going to go out of the windows.

Also is it worth doing the floor, I am going to put a floating floor it, is it worth green glue in between the styrofoam/chipboard?

Any advice, please.

[Jazz Monkey Jr]

Would is be a good idea to put 2 double gazed units to keep the sound in? Would they need to be toughened?

[mattym]

the window i dont know about, but the floor, if you put green glue down in the same way as your wall, sandwiched between layers, it will work best that way

[Jazz Monkey Jr]

Originally Posted by mattym

the window i dont know about, but the floor, if you put green glue down in the same way as your wall, sandwiched between layers, it will work best that way

It is going to be a floating floor, so I would put it between the floor insulation (syrofoam) and the chipboard?
Also how much is the green glue, I reckon I will need 40 sheets of soundblock (doubled up) so that will be 40 tubes of green glue (2 tubes per sheet) which is 4 cases.