I am building an addition on our house (1,163 living and 684 garage). Right now we are in the process of framing the house. The architect called for stucco, osb sheathing, insulation, vapor barrier, then drywall. When designing the addition I told the architect my main two considerations were energy savings and low cost. I am wondering if he didn't spec exterior foam for due to added costs and if I can still add a thin layer of 1/2 or 3/4 inch foam to help prevent thermal bridging? Also I have had three coats from stucco contractors and they all said they lay two layers of felt on the osb (water barrier), lathe, then three coat stucco. Is the lack of rainscreen (drain vent) concerning? I asked about a rainscreen like Tyvek Stuccowrap or Benjamin Obdyke Slicker Max and they look at me like I have a third eye. I do live in a desert (Zone 14). Thanks!

are you using 2x4 framing? there are formulas for how much exterior foam you need and it depends on your location (humidity levels I believe) and how much interior insulation you have. It's a ratio you have to deal with and you can't just slap too little exterior insulation and think you're ok. I had another post somewhere on here where Dana1 (I think) gave info on how much exterior insulation I needed based on my zone for my mud room.

Anyway, I'm not an expert on these things, but I have learned a few things from the helpful folks here.