Exterior insulation and finish system (EIFS) is a general class of building cladding systems providing exterior walls with an insulated, water-resistant, finish in an integrated composite system.
In Europe, systems similar to EIFS are known as External Wall Insulation Systems (EWIS) and External Thermal Insulation Cladding System (ETICS).
The most important elements of an EIFS are:
- an insulation board, typically made of expanded polystyrene (EPS)
- a reinforced layer (base coat) applied to the face of the insulation with a trowel, consisting of a fiberglass reinforcing mesh embedded in a dispersion-based adhesive
- a final topcoat, or finish, which is colored and textured.
The basecoat, with embedded fiberglass, needs to offer mechanical and fire protection to the expanded polystyrene sheet. This means it needs to provide sufficient impact resistance as well as flame retardant properties. As the coating layer with the highest film build, it contributes most to the flame retardancy of the EIFS.
The formulator needs to find a good compromise between these properties – selecting a suitable binder with good outdoor performance and low caloric value, as well as the right filler combination.
For ETICS/EIFS applications, the most important filler is ATH which provides:
- Flame retardancy: the main role of ATH is to release water at 180°C to extinguish the starting fire, or at least slow down the burning process.
For benefits other mineral fillers can bring to ETICS applications, see Architectural coatings – Exterior.