The component that makes EIFS the foam

One major material that makes Exterior Insulating Finishing Systems different from all other wall cladding systems is the insulating foam. In fact, the foam is what makes it an EIFS, and without it it would be merely a wall coating.

The foam, usually composed of expanded polystyrene (EPS) offers many other functions as opposed to simply providing thermal insulation to homes and buildings. EIFS can use other insulations, such as the mineral wool insulation that is popular in Europe, but in Canada the material used most often is EPS. Fibrous, ceramic and foam plastic insulations may seemingly have positive attributes that they can bring to improve EIFS, but a close examination and breakdown of these materials’ composition and qualities reveals otherwise.

Ceramic and foam plastic insulation

EPS is strong and flexible, while other forms of insulation may break easily or not have as much “give”. Without this give, the EIFS would not have the necessary flexibility that prevents the lamina from cracking when the wall upon which it is clad shifts. The softness and flexibility of the EPS also allows it to move independent of the surrounding layers, preventing further cracking or disturbances to the lamina. Its exceptional give helps prevent the EIFS from cracking upon external force or impact as it is a much springier material than others that are available, such as ceramic and foam plastic.

Ceramic insulation is available for EIFS applications, but is really only used where noncombustibility of the building envelope is an absolute requirement.

Foam plastic, such as extruded polystyrene, is slightly softer than ceramic, which is quite breakable, but foam plastic is not nearly as flexible as EPS. Foam plastics are also especially flammable.

Fibrous insulation

Semi-rigid board, or fibrous insulation, is relatively weak when compared to EPS. This weakness is a prime factor in why it cannot be used in certain buildings that may face excess wind, which can tear it up with ease.

It is also textured in such a way that the liquid-applied coatings would have much more trouble effectively sticking to fibrous insulation than they would EPS, and it’s difficult to make them into a smooth wall. If it were to be used in an EIFS application, the coating applied to it would have to be extra-thick, at which point the total weight becomes a significant issue, and the coating would have to be supported separate from the insulation.

Fibrous insulation is far less dense than EPS, which can lead to far more serious water and moisture retention problems as water vapour can penetrate it more easily, allowing condensation to form.

Drawbacks to EPS

The major drawback of EPS is that it is a combustible material. This issue can be rectified in many different ways, such as using a non-combustible coating, incorporating reinforcing mesh that is noncombustible and back wrapping the edges of EIFS, preventing fire from reaching the EPS core. Despite the combustibility of EPS, EIFS are still used on buildings and homes with stringent fire codes because the installation of EIFS does not detract from the preexisting fireproofing of the supporting wall.

While many times over, the industry has tried to develop a material that retains all of the positive qualities while doing away with all of the negative components of each different form of insulation, but hurdles such as cost and effectiveness arise. EPS has already proven itself as the ideal form of thermal insulation for EIFS applications, and proper installation, reinforcing and proper back wrapping can assist in mitigating the negative qualities like combustibility.