Structural silicone glazing

A guide to field installation and design practices

By Christopher J. Brandmeier, PE, Bradford S. Carpenter, PE, and Sierra L. Scott

Structural silicone glazed (SSG) façade systems are an industry mainstay. Contemporary prefabricated and unitized systems that leverage SSG technology have come to supplant earlier field-fabricated and stick-built systems that typically limited the use of field-installed SSG glazing, often using SSG only in combination with mechanically captured pressure bars along vertical or horizontal edges.

Contemporary prefabricated SSG façade systems continue to push the envelope of possibility and performance through incorporation of technological advances in materials, thermal and energy performance, air and watertightness, structural performance, fabrication techniques, and sustainability considerations resulting in a seemingly limitless variety of forms and functions. These advances allow SSG façade systems to suit an increasingly wide variety of building types and climates, leading to increase in market share of new construction projects and a corresponding rise in need for field-installation of SSG to accommodate sequence of installation, construction breakage, or material issues arising out of the new construction. In addition, SSG façade systems typically have a service life of 20 to 40 years and are usually dependent on the service life of the glazing materials. As a result, the growing number of aging in-place SSG systems present an increasing need for in-situ renewal and glazing replacement.

These SSG elements that were originally assembled under the clean and controlled environment of a fabrication shop face an increasing need to be reliably replaced in the more challenging environmental and logistical conditions presented by an existing in-place building façade.

Whether it be field installation of SSG on new construction projects or the replacement of SSG insulating glass units (IGUs) with an eye on the sustainable service life extension of an existing façade system, the demand for field installation of SSG is growing and presents unique challenges for owners, designers, and contractors.

Specifically, with field-installed SSG, the authors have found many project stakeholders expect factory-quality installations of SSG consistent with prefabricated or unitized façade systems of new construction and frequently underestimate the difficulty of achieving the same results in field installations. The gap between expected quality and realized quality represents a challenge for all parties involved and is an opportunity for improved understanding and practices in both system and SSG design as well as the quality control and quality assurance of installations.

This article provides project stakeholders and designers with a discussion of principles and methods for improving the quality of field installed SSG, from the perspective of design (i.e. to accommodate realities of construction), specification (i.e. of appropriate sealants, installation methods) and quality control and quality assurance procedures (inspection, testing, documentation). The scope of this article is limited to field-installed SSG and does not address operational lifecycle maintenance of SSG or alternate methods of achieving field installations of SSG such as use of toggle-style cassette systems; both of which are important considerations worthy of attention.