The Three Ps of Prefabricated EIFS
Preparation, Production, Placement
In its most general form, exterior insulation and finish systems (EIFS) consist of expanded polystyrene (EPS) insulation board coated with a reinforced polymer-modified cementitious base coat and a polymer-based finish coat. Other less commonly used types of rigid insulation boards in EIFS include extruded polystyrene (XPS), polyisocyanurate (polyiso), and mineral wool. Drainage EIFS, unlike barrier EIFS, includes a dedicated water-resistive air barrier (WRAB) and drainage plane.
EIFS is lightweight and uses relatively few materials. It is typically adhered in place, eliminating cladding anchorage penetrations through the WRAB. EIFS-clad wall panels can be fully prefabricated, from the structural backup to the finish coat. EIFS adhesives, typically polymer-modified cementitious materials, are compatible with many WRAB chemistries. EIFS provides continuous insulation (c.i.) on the exterior of the building, which increases the effective thermal resistance of the assembly. EIFS can be readily sourced from several manufacturers, many of which have already performed a myriad of assembly tests, including fire performance, bond strength, impact resistance, and drainage efficiency, among others, and obtained assembly approvals in major jurisdictions. EIFS is also a cost-competitive cladding in many markets. As a result, EIFS has become an attractive cladding option for use in prefabricated wall panels, in which EIFS materials are shop-applied to sheathing and metal stud backup wall construction under controlled conditions. Prefabricated panels may also include fenestration and other elements of the exterior wall.
Despite its potential benefits, EIFS has limitations that must be considered when used as a prefabricated wall panel cladding. By having continuous and often flammable insulation on the exterior side of the wall, EIFS is susceptible to melting, ignition, and fire propagation. It is prone to impact damage during transportation, installation, and service, particularly at panel edges. Where field repairs or modifications are necessary, it can be challenging to repair the prefabricated panel in the field in a way that restores WRAB continuity and provides a matching finish texture. While fully adhered systems offer certain advantages, their water management performance depends entirely on the quality of the installation, specifically, the quality of the drainage plane, which is rarely verified. As with any prefabricated panel cladding, joints, and transitions to adjacent enclosure systems require significant forethought and planning while considering constructability in the shop and the field.
One can realize the schedule and quality benefits of prefabricated EIFS-clad wall panel construction by following the three “Ps”: ensuring appropriate scope and detailed design during “Preparation,” implementing robust quality assurance and control processes during “Production,” and executing effectively during “Placement.”’
Publisher
Construction Specifier