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).
What can cause this delamination to occur? The sources are many, but a few are key.
Heat of the momentHere is a basic list of factors that can contribute to this situation.
Color is perhaps the key issue. The darker the color of the EIFS finish, the more likely the problem will occur. Dark colors absorb more solar radiation (heat) than lighter ones. Lighter colors reflect more energy, hence staying cooler. When directly backed up by insulation (i.e., the heat has no where to go except to build up in the lamina), it's easy to see how the temperature of the thin EIFS lamina can easily skyrocket to the point that it overheats the adjacent foam.
Geographic location is an issue too. A high altitude and a clear sky increase the level of sun exposure. There's not much to worry about in overcast areas like Seattle, but in clear, sunny, high-altitude Tucson, it is a real concern. But beware, I've seen this problem in Michigan; no area is truly immune.
The orientation of the building is also an issue. Clearly southern- and western-facing façades tend to get the hottest and these sides are usually the first to feel the effects.
Reflective surfaces can also contribute. Shiny nearby objects (like polished metal walls, bright roof surfaces or mirror glass) can give the lamina an extra temperature boost, aggravating the problem. Skylights and shiny rooftop equipment can also focus energy on the wall, resulting in localized, or even widespread, lamina delamination problems.
If you suspect that the delamination you see on an EIFS wall is caused by overheating, here's a way to be sure. Mount some temperature sensors on the EIFS lamina and see how hot it really gets. You're looking for the maximum temperature, so you'll need a recording system to save the data, without someone standing next to the wall endlessly.
Keep it coolHow to fix such problems? If the lamina is free and clear, then it can be removed with zero effort. The problem is that the delamination will not occur evenly. At the edges of the EIFS and at areas not directly exposed, the lamina will often still be fine. This means that the whole lamina in the affected area must be stripped but there will be adjacent, thicker areas that are still OK. The problem is that most EIFS walls are flat and the insulation in the overheated EIFS areas will be thinner, requiring that adjacent areas be brought to the same thickness. Not a cheap task (rasping a huge wall area can be an exercise in frustration), but removing an entire wall area is sometimes the only way.
And it's not just the lamina that must be removed. More than likely, the foam must be removed back to the substrate. This foam removal process, in turn, often ruins the substrate.
What is the bottom line on this matter? The answer is multi-fold. First, for contractors, be suspicious of dark colors and explain to the "color chooser" what the implications are. Second, make sure the architect or engineer knows about this in terms of the design of the building (solar orientation, color effects, etc.). Third, be aware of nearby architectural materials that can reflect light and zap the lamina. Finally, do not get too crazy about this rare phenomenon, but keep it in mind as part of your repertoire of deep EIFS knowledge ... to impress your clients and to do a better job.