Dryvit is synthetic stucco. Usually a foam sheet backing over some type of sheathing, with various grades of fiberglass mat over the foam, depending on how much puncture resistance they need. Tougher at ground level, softer at inaccessible areas. The actual coating is an elastomeric (non-breathable, with elastic properties) type coating with sand or other aggregate mixed in to give it the stucco look. Its the same stuff that has been the subject of class action suits in residential construction, because of improper installation and lax supervision and detailing in residential vs commercial.
The problem with synthetic stucco systems is that they sometimes create a vapor barrier on the exterior of a structure -- which leads to moisture being trapped between the inner vapor barrier and the exterior cladding, which can then become an ideal growth medium for microbial and fungal organisms.
In the mid 90's, one of the Carolinas banned synthetic stuccos -- they found that moisture could even enter the wall through wood window sills, one of many ways the system could be compromised.
If synthetic stuccos are installed with vapor relief channels behind the styrofoam substrate, they will vent off moisture in the same way conventional construction breathes. But most of the installations in the 1990s were styrofoam glued onto exterior sheathing -- which means that the system is only as good as it's overall prevention of moisture entering the structure.
In Colorado, most builders have gone back to using traditional stucco, which is a sand and cement plaster -- which is permeable to water vapor, and thus avoids the potential problems of faulty synthetic stucco installation.
