Insulated metal panels (IMPs) are a popular and practical way to provide a complete exterior wall system on many different building types. But what if a building design calls for some other type of cladding or outer covering besides metal? Does that mean only conventional construction can be used with multiple layers, multiple trades and multiple areas for potential problems? Actually, it doesn’t. Instead, a version of an IMP can be used that is specifically intended to be used as part of a rainscreen wall system with virtually any type of exterior cladding. Referred to simply as BW (Back up Wall) Systems™, it offers all the practicality and benefits of an IMP plus the flexibility of allowing for any exterior appearance.

BW panels are manufactured like most IMPs using a layer of polyurethane foam sandwiched between an interior and exterior metal skin. Since the metal is intended to be covered over with other materials, the surface of BW panels is simply factory-primed and left plain, making them more economical than a fully finished panel. The edges of the panels are formed into a double tongue-and-groove profile making it easier to seal the panels tightly together. The panel systems are installed either horizontally or vertically with a concealed face fastening aluminum rail that fits along the edge of the panel and provides the means to secure the cladding.

Incorporating BW Systems™ into a building design instead of relying on conventional construction takes advantage of four impressive characteristics:

• One-step for all building envelope control layers – air, water, thermal and vapor All of these barriers are required by building and energy codes and for a good reason. If any of these are missing, the building will perform poorly and may have its useful life shortened unnecessarily. Conventional construction relies on the use of different materials to achieve these barriers. Air and water barriers are placed in the field over an exterior sheathing substrate; thermal insulation is placed either between or over structural framing (or both); vapor barriers are most commonly applied on the interior of framing. Backup Wall systems combine all these control layers into a single product. The exterior metal face provides the air and water barrier, the rigid insulation is the thermal barrier, and the interior facing (liner panel) acts as the vapor retarder. The overlapping tongue-and-groove profiles help assure continuity of these barriers and is enhanced using long-lasting butyl sealant along all the joints.
• Allows multiple facade options The BW System™ is a fully prepared substrate and mounting system for virtually any exterior cladding. Such cladding can include brick, concrete , metal, composites, or terracotta, among others. Since the BW panels are installed and sealed first and provide the performance part of the wall, the choice of exterior cladding does not reduce thermal efficiency or the integrity of any of the other control layers. Hence, performance is maintained, regardless of what the exterior cladding or look of the building is. This is a huge advantage for buildings that use multiple claddings to create a more dynamic or diverse look. Typically, each change in façade material would require special attention to assure continuity and integrity of the various barriers. With a BW System providing the continuity, all those potential issues are eliminated.
• Easy and fast installation Each of the conventional control layers can require separate materials, separate trades, separate scheduling efforts and separate inspections. That means more time, more labor and more cost. Backup Wall systems streamline all of those, reducing the time and cost of construction, materials and labor. Since it is a one-step, single source system, project management is simplified as well.
• Encloses the building faster Getting the building enclosed quickly is often a high priority for many projects. The streamlined, one-step process of BW systems clearly help in that regard since the BW panels are durable enough to be exposed temporarily until the final cladding is installed. Meanwhile, the interior is protected, warm and dry. Further, the BW panels are not bothered by weather during installation so rain, heat, cold, and other conditions are no longer a reason to stop construction and send crews home for the day. Instead, the installation can continue unimpeded, as long as high wind is not disrupting panel placement.

Backup Wall systems are ideal for virtually any commercial or industrial building including schools, manufacturing facilities, distribution warehouses, equipment maintenance buildings, retail buildings, medical buildings, aircraft hangars, office buildings, and any others where façade design options and excellent performance are being sought. For more information about using backup wall systems on a current or future project, visit the Metl-Span website or contact your local Metl-Span Business Development Manager.