We are just starting a design for a one-story 14,000 sf Ambulatory Surgery Center (Type-III Building) just east of Sacramento. The wall design is going to be a cementious stucco on lath over building felt on a Dens Glass sheathing over 2 x 6 metal studs with 6 inch fiberglass batt insulation and 5/8 inch Type X gypsum wallboard. The geographical location of the building has me concerned with regards to the placement of a possible vapor barrier. We have not designed a building in a Hot-Dry region before and some of the information I do find shows multiple methods. Just wondering if a vapor barrier is used typically? Is the barrier semi-permeable? Location of the barrier? Looking for recommendations. Thoughts?