conditioned space over unconditioned garage – retrofit – GreenBuildingAdvisor

I have a structure with an unconditioned garage with conditioned space above and to one side. It’s down to the studs at the moment. And the way it was built (not by me), it will be near impossible to air seal within the cavities between the conditioned and unconditioned spaces. How critical is this? And if critical, what are some ways to do this?

Climate Zone 5

My plan was to use sheep wool batts in the wall cavities, rockwool in the garage ceiling, intello all the conditioned faces, and vapor permeable mento the walls and ceiling of the garage. Will that work?

Also, I could sort of block off the space above the garage so that it is only sort of conditioned, but there is a window in that space and I’m hoping to not block the light from coming in to that space and the main space below (next to the garage). So I could sort of block the heat with a sheer curtain or acrylic-type doors or something.

And just for my understanding of theory – is there something different about the air in the cavity above the garage versus below the garage? Isn’t it cooled the same by the same exterior air above and below the floor?

Also the exterior walls have ci (rockwool), an air gap, and steel siding, if that’s relevant.