Galvanic action
For galvanic action to occur in steel curtain wall assemblies, the steel must be in direct contact with dissimilar metals. This is most likely to happen when design professionals specify steel curtain walls with aluminum pressure plates to achieve a specific esthetic. Fortunately, the configuration of some advanced steel curtain wall systems can help prevent aluminum pressure plates from coming into direct contact with carbon steel framing members.

For example, suppliers can use stainless steel screws to connect the aluminum pressure plates to steel back members. Stainless steel is closer to aluminum in anodic polarity, thereby reducing the potential for corrosion to occur. Steel curtain wall manufacturers and suppliers can also coat metals with a non-conductive paint or finish. This helps effectively isolate the two dissimilar materials.

An alternative method to reduce the potential for corrosion between dissimilar metals is to form the framing members from stainless steel alloys. Series 304 is typically the only stainless steel alloy used in the rolled-profile methodology (many other alloys are too brittle). Other stainless steel alloys may require significantly more fabrication time. For example, the 316 series requires slower saw and drill speeds, which increases fabrication time. As a result, a best practice is to check with fabricators prior to specifying a stainless alloy.

Before installation
The exterior walls of a building define its looks. With proper specification, advanced steel curtain walls can help design teams meet modern design demands, and provide assurance they will look beautiful for years to come. This requires careful due diligence and review of architectural drawings, specifications, approved shop drawings, and manuals well in advance of pricing and installation.

Each steel curtain wall framing system is subject to different project conditions, from its specific environment to mullion spacing and glass size requirements. As with any assembly, reviewing these details is crucial to moving forward with a design approach protecting the framing’s long-term appearance. For example, it is important to verify the amount of deflection does not compromise the strength of the steel members, causing bowing, sagging, or joint failure. This will also aid in protecting glass lites from being forced out of place.

A final step is to consult the manufacturer or supplier’s specific installation instructions. As evidenced throughout this article, advanced steel curtain wall systems have a different set of considerations than aluminum curtain wall systems in some areas. Additionally, products vary by manufacturer. Assuming standard practices may result in incorrect installation, particularly regarding air and water integrity, and risk the manufacturer’s warranty from being extended. Many manufacturers are more than willing to provide design and installation support, and aid in creating steel curtain walls that are attractive for years to come.

Chuck Knickerbocker is the curtain wall manager for Technical Glass Products (TGP), a supplier of fire-rated glass and framing systems, along with specialty architectural glazing products. With more than 35 years of curtain wall experience, he has successfully worked with numerous architects, building owners, and subcontractors from development of schematic design through installation. Knickerbocker is the chair of the Glass Association of North America (GANA) Building Envelope Contractors (BEC) Division Technical Committee. He can be contacted via e-mail at chuckk@tgpamerica.com.