I started my video career by planning, designing and selling studios and equipment to corporations and colleges.
What Mark is saying is absolutely true. However I’d change the order slightly:
Sound proofing
Power
HVAC
Lighting
I’d put lighting last on the list, because with proper power, you can always add lighting.
Originally we build a studio for a major fast food company. Within the studio we build wall flats that we could use to create the dining room of a fast food restaurant, including booths, tables, chairs and the nicknacks for the walls and tables. We also built a tile wall for those quick kitchen-looking shots.
Of course we had a 30′ X 40′ studio space to work with.
Then we build a control room/edit suite with a tech/equipment room to house all of the equipment power supplies and fans so the edit suite and studio would be quiet.
We built walls as Mark suggested, and had extra wide HVAC ducts installed to minimize sound. Finally we installed special sound absorbent doors to keep exterior sound from the company’s individual departments to a minimum. Lastly we added in a small portable VO set-up to record clean narration.
Mush depends on your budget, but when we moved to a new building, the construction budget was included in the total construction budget. You should consider hiring a consultant to work with the construction company.