Improve the Fire Performance of EIFS
of the building, such as a hospital or laboratory building or a computer center, where the building envelope needs extra attention.
When EIFS first came onto the scene in the United States in the '60s, one of the hot issues was its performance in fire. Initial usage of EIFS was mostly on commercial buildings, which, according to the building codes, usually have to be made of noncombustible materials. EIFS, both the foam plastic insulation and the coatings, are not noncombustible.
After many years of fire testing and working with the code people, ways were found to qualify EIFS so that it can be used on buildings that are required to be noncombustible, even though EIFS is not noncombustible. Aside from meeting the code requirements for fire performance that apply to EIFS, such as running various large scale fire tests, there are other things that can be done to EIFS that will improve its performance in fires and particularly on multi-story buildings. Here are some of the key ones.
Fuel contentMost of what can burn in an EIFS is the foam plastic insulation portion of the EIFS. The codes limit the amount of insulation to 6,000 British thermal units per square foot. A Btu is a common measure of heat energy. This 6,000 Btu number is called the "fuel content" and is a measure of the energy that would be released if the foam were burned completely. For the 1.0 pound per cubic foot density EPS foam commonly used in EIFS, this 6,000 Btu number equates to a maximum of 4 inches of foam. Obviously, one way to enhance the fire performance is to use thinner foam. Conversely, the use of thick foam shapes can exceed the 6,000 Btu limit and thus such uses need to be discussed with the code people on a project specific basis.
Floor linesOne of the main concerns on multi-story buildings is the issue of fire spreading from floor to floor. In the case of an EIFS-clad wall, this flame migration could occur around the edge of the floor slab, within the stud cavity, within the EIFS foam core, and on the surface of the EIFS. One foolproof way to keep fire from burning within the foam core is to stop and start the EIFS at the floor line. This means simple putting an expansion joint all the way through the EIFS and the supporting wall structure. Another way, which is done in Europe but not much in the U.S., is to put some type of noncombustible insulation within the EIFS foam layer at the floor line. This can be difficult to execute, as the change in insulation type can induce cracking in the EIFS lamina. This solution needs to be discussed in detail with the EIFS manufacturer.
Window headsFire often exits the room of origin through windows. The flame plume attacks the window head, burning the EIFS. It is important that the EIFS remain intact at this location, lest fire get into the foam core. The usual way to seal the edge of an EIFS is to backwrap it. Since the glass reinforcing in the basecoat has good high temperature properties, it can withstand the fire. Problems can occur if techniques other than backwrapping are used.
For instance, aluminum melts at a fairly low temperature and plastic trim melts readily. Also, if an EIFS with drainage is used, there may be a drainage opening at the window head, which could be a point of flame entry.
Alternate insulation typesIn some parts of the world, combustible forms of insulation, such as any type of foam plastic, are simply not permitted on certain types of buildings in certain areas. For instance, in crowded urban settings with lots of tall buildings in some European cities, plastic foam-based EIFS is not permitted. In this case, EIFS that uses noncombustible types of insulation, such as mineral wool, are used. Mineral wool-based EIFS is rare in North America but clearly solves the fire problem in a very direct way.
Securing the EIFS to the substrateWhen EPS-based EIFS are involved in a fire, the heat of the fire quickly passes through the EIFS lamina and melts the foam behind it. The molten foam is a liquid and can flow. It's therefore necessary to keep that molten foam within the EIFS. So, once the foam has melted there is nothing holding the EIFS lamina to the substrate, it's important that the edge of the EIFS be securely attached to the substrate. In a nutshell, this means that the edge of the EIFS must be backwrapped, especially at areas above where a fire would reach the EIFS.
Soffits and ceilingsIt's not uncommon for a soffit or ceiling to exist directly outside of a window or door. If EIFS is used as the soffit material, it is literally hanging upside down from the substrate. If a fire attacks the EIFS, the foam will melt quickly and the soffits will have no means to support itself and could collapse. This is the reason why large soffits can be dangerous in fires: They sag under their own weight and would tend to fall apart.
Adhesives and meshesEIFS basecoat and attachment adhesives have some affect on fire performance. Adhesives that use Portland cement are slightly less combustible than those that are noncementitious. Similarly, a basecoat of proper thickness (i.e., not too thin) affords greater protection to the foam, due to its greater strength. Likewise, heavier grades of reinforcing mesh give additional fire resistance.
Fire resistance ratingThe term "fire resistance rating" has to do with the number of hours a wall assembly can withstand a fire. The key concept to keep in mind is that EIFS provides no fire resistance and that the supporting wall alone must be able to provide all the required fire rating, such as a 1-hour wall and so on. The addition of EIFS to a supporting wall that has a known fire rating does not change the fire rating of the wall assembly for the better or worse.
Indoor use of EIFSThe codes require that if foam plastic insulation is used indoors, than the foam must be separated from the interior space by a material with a 15-minute fire rating. An example of a material with that rating is 1/2-inch gypsum wallboard. However, the EIFS lamina is too thin to provide the required 15-minute protection. This is why EIFS should not be used indoors.
Heat producing devicesMost brands of EIFS use EPS foam insulation. EPS has a low maximum service temperature; EPS starts to melt at around 175 degrees F. One wants to keep EPS away from sources of heat, such as light bulbs, exhausts, transformers and so on. Be careful when using EIFS as a cladding on chimney enclosures, such as the prefabricated metal ones that are usually surrounded by wood framing and sheathing.
SubstratesThe use of noncombustible substrate materials can improve the fire performance of EIFS-clad walls. Heavy materials, such as concrete and block, work best but gypsum-based sheathing is more fire resistant than wood ones, such as OSB and plywood.
Considering the lightweight and combustibility of EIFS, the system performs impressively in fires. The fire tests developed by the EIFS industry in the last several decades appear to characterize accurately the way EIFS performs in real fires. This is evidenced by a number of major fires that have occurred on real EIFS-clad buildings and the fact that the EIFS performs as expected. It's interesting to note that the issue of EIFS fire performance is mostly one for commercial buildings. In wood frame buildings, such as most houses and many apartments and condos, the whole structure is combustible, and hence the presence of EIFS represents only a fraction of the fuel in the building.
In terms of using the above information, the points made are primarily design-oriented. Thus, if working on an EIFS project that has special concerns about fire issue, the points above are worth discussing with building designers so they can be incorporated into the drawings and specs for the building.