Stucco is a wonderful material to create a vapor barrier on the exterior of a building. It's breathable (so moisture can escape from the inside), yet waterproof (so rain and moisture doesn't get through the exterior wall). It's been around for thousands of years, so it's tried and true, and yet you can make it a variety of textures and colors. You can put a rain screen on top of it (for both aesthetic and functional reasons), or leave it to stand on it's own. The best part is the simplicity - lime, water, sand, and tint - all simple inexpensive old materials - which can be as modern and contemporary as needed.