This month's column is about what happens when an EIFS gets too hot.
Most EIFS use EPS (expanded polystyrene) insulation. EPS has a maximum sustained working temperature of about 165 degrees F. When the EPS get hotter, it melts. When it melts, it recedes back from the heat source, creating a gap between the lamina and the EPS; the lamina is thus "loose." The lamina ends up hanging there like a curtain.
Keep in mind that this behavior applies to polystyrene insulation, like EPS and extruded polystyrene (Styrofoam), both of which are a type of plastic called thermoplastics. Thermoplastics melt as they get warm, rather than all of a sudden getting fried. Other types of plastics, notably the thermosetting types, do not melt, but rather get hot, and then degrade suddenly. Thermosetting plastics are urethanes and polyisocyanurates (such as the Quik-RTM types use in some EIFS).