The Finish Line: EIFS du Jour
CULTUREPerhaps the driving force of the difference between North American EIFS and EIFS in Europe comes from the culture. Europe is simply much older and has a lot of serviceable, old, solid masonry buildings that need to be better insulated. Since the walls that support the EIFS are solid, there’s no cavity to put the insulation in; new insulation either has to go indoors or outdoors. Inside insulation takes up floor space, but lets the wall retain its current exterior appearance. Exterior insulation changes the look of the facade, but doesn’t intrude into useful interior space. It’s thus easy to see why EIFS is popular, especially if the old walls are leaky. Plus, you don’t have to leave your house while the re-insulation project is underway.
There’s also the point of view in Europe that buildings are supposed to last for generations, and hence should be robust – no “throw away” architecture on “The Continent.” In America, I see the viewpoint toward buildings of being more utilitarian and investment oriented, rather than part of the charm of the area (American EIFS houses that look like out-of-place chateaus, or some place where Shakespeare was born, etc.) There is a higher percentage of government-sponsored housing and multi-family units in Europe, too, and both building types are expected to last a long while to meet finance and insurance requirements. A client from Europe once remarked to me that he did not understand why people lived in wood houses, when “over there” they see such wood structures as being for barns and animals. Lightweight wood or steel framing is much less common in Europe. Most mid-rise buildings have masonry walls, and ultra-tall buildings are few and far between. If stud cavity wall systems are used, then cement-or-mineral-based sheathings are often employed; gypsum-based products are seen as more of an interior “lining” product than as a structural exterior sheathing.
BASE COAT THICKNESSThe thickness of the base coats of most European EIFS is about twice that in the USA. This translates to a stronger wall that is more resistant to water penetration. It also leads to higher costs. This increased thickness also is needed to pass the rigorous tests required by various countries’ governments to qualify the EIFS as a “good product.” This “approval” process is somewhat akin to the Evaluation Reports issued by the International Code Council in the USA, but the tests are more demanding. Interestingly, some of the European tests have been adapted as the basis for standardized EIFS testing in North America, such as occurs via the ASTM organization.
MECHANICAL FASTENERSIn Europe, the use of EIFS as a retrofit material is more common than in North America. Often, the substrate is stone or masonry, and sometimes these substrates either cannot be reliably bonded-to with an adhesive, or they are not completely sound. Therefore, mechanical fasteners, in the form of barb-ended solid plastic pins (without a screw) are pounded into pre-drilled holes. Even though the fastener is all plastic, it does create a thermal bridge through the insulation layer, causing a change in color on the finish which comes and goes as the moisture level and the temperature of the EIFS lamina changes during the day. To get around this unattractive appearance, shallow, round pockets are first augured into the foam so that the washer head of the fastener is recessed when the fastener is pounded in. Then, a round EPS cap “plug” is press-fitted into the hole, covering the fastener. By doing this, the thermal bridging is substantially reduced. The cap plug is slightly thicker than the depth of the hole, so it protrudes past the face of the foam, but is rasped to make it flush. A similar bury-the-fastener-under-foam approach can be done with fasteners that use a plastic washer and a metal screw.
EMBEDDED TRIMThicker base coats allow handling the perimeter of the EIFS more easily in the sense of using embedded trim to get a straight, hard edge, and not having to back wrap the edge. The extra thickness allows getting the trim solidly embedded, so it doesn’t work loose over time. Specialized trim designs are available just for EIFS, including stainless steel and zinc.
HIGHER RESIN LEVELSIn Europe, the percentage of resin in the base coat adhesives and finishes is higher than in the United States. It’s quite normal to see 80/20 adhesive/cement ratios, as well as cementless adhesives. The 50/50 ratio common in North America actually came from the first EIFS products that were imported from Europe to the U.S., but were made more “cement rich” to reduce cost. They still work OK, as long as the in-the-pail adhesive itself has a high percentage of resin (i.e., not much filler). Higher resin levels generally give all around better performance. In some places in Europe, the percentage of resin is displayed on the pail, thereby giving the consumer some idea of what you’re getting in terms of quality. The problem is that resin (and resin blends) is not all the same, so this type of “truth in advertising” can be misleading.
EIFS, SOLD AT ‘MAISON DEPOT'In some parts of Europe, you can buy EIFS at the Jacques and Marie’s local quaint hardware store. Although not a DIY material, even in Europe, it’s common enough to be sold at retail. I can’t imagine what would happen if EIFS was sold this way in the United States to the masses via the Big Box home improvement stores. Lawyers would have a field day. At this point in history, I’m of the mind that EIFS needs to be installed by professionals, just as you wouldn’t let the handyman’s nitwit nephew install elevators.
SOLID SUBSTRATESThe recent trend toward EIFS-with-Drainage in North America raised the eyebrows of my European clients. They didn’t quite understand why we needed drainage until they realized that the supporting wall is often made of wood or other moisture-sensitive materials. They don’t understand why we don’t use more durable materials, such as masonry, as the substrate, as it would offer the additional advantage of a heavy wall to hold the heat by virtue of the external location of the insulation.
SIMPLE DETAILINGThe European’s are intrigued by our use of foam shapes, especially since they are sometimes used to “fake” an old European style, such as a “villa look” or impress-your-neighbor “mega-home castle.” But functionality rules in Europe and their walls are usually flat and unadorned, and they use simple, robust details to keep the weather at bay. In particular, the use of heavy metal or even fiberglass flashings is the norm in lieu of excessive reliance of sealants alone. And if the wall does leak, the masonry substrate would hardly be affected anyway.
NONCOMBUSTIBLE INSULATIONThe building codes in Europe tend to be more conservative than in North America, especially in terms of fire safety. The higher population density and the more widespread use of multi-family urban housing means that you have to be extra careful of what might happen if your neighbor’s place caught fire. This approaches continues to wall claddings, most of which are noncombustible (i.e., do not burn at all) – such as stone, brick, tile, and traditional stucco. Since many modern EIFS use combustible foam plastic insulation, its use is not code compliant in some built-up areas. EIFS systems that use mineral wool insulation, like that which is used for fire stopping, are available in Europe. This is a specialized material in the form of mineral wool (i.e., not a batt) of small blocks that have one face ‘toasted” to create a “crust” over which metal lath and real stucco are applied. Yes, metal lath is mechanically pinned through the mineral wool into the masonry substrate, and stucco is put on the outside. This results in a completely noncombustible wall that is a real EIFS. Pretty cool, but not cheap.
LESSONS LEARNEDThere is much we can learn from the extensive experience and different points of view about EIFS from our friends in Europe. It continues to surprise me that we in North America seem to be “stuck” on EPS-based systems when different systems with specialized qualities might be better for certain applications. There are even such things as spray-on foam insulation (no attachment adhesive needed, and goes over wavy substrates – great for retrofitting) and one-coat, spray-on combination base coat and finish.
For the life of me, I wonder why someone is not giving these types of systems a hard push into the North American market. Having worked with these systems, the key seems to be cost and design flexibility, and the current popular type of EPS-based EIFS seems to be the best overall way to do EIFS, hence its rampant popularity.