Expanding high-performance designs
When channel glass basics are well understood, it is possible to use the material as a high-performance aesthetic alternative to conventional glazing. The following channel glass configurations show how building professionals can use it to preserve critical performance goals while pushing a building’s form.
Continuous glazing spans
Design professionals can specify long, linear sequences of channel glass to achieve greater heights and create large, dramatic glazed areas. In vertical applications, unsupported cast-glass channels can span up to 7 m (23 ft) without interruption. They enable sophisticated façades and storefronts that let in significant amounts of daylight or create visual interest with bold colors and backlighting.
When specifying channel glass for these tall, sweeping glazed walls, it is important to note a building’s design-imposed wind loads will determine the channel’s maximum length. As such, one should consider consulting with the manufacturer or supplier early in the design phase to determine how design loads may impact the desired aesthetic.
For example, in instances where wind loads limit the length of single-glazed channel glass segments and constrain the design intent, it is possible to split the elevation to achieve the desired outcome. This process requires adding a structural member at or below the upper height limit for the desired wind load to create separate openings, which are then used to individually frame in an extruded aluminum perimeter frame, creating two openings. Since the intersection of the two openings—known as a stack joint—is often more pronounced than the surrounding channel glass framing, design professionals may elect to cover it with decorative cladding.
Alternately, for dual-glazed systems in vertical applications, wind-load anchors can provide the necessary structural support. Wind-load anchors consist of a small T-shaped face plate and back plate, which sandwich the front and back edges of the glass. The wind-load anchor runs between the overlapped cast-glass channels, attaching to a structural element behind the glass wall. This creates a secondary fixed support that minimizes deflection, allowing for a taller, continuous span of glazing. As an added benefit, wind-load anchors can save on installation costs by reducing the framing and glazing required to meet wind loads in a given opening.
Long-length installations
When using horizontally glazed cast-glass channels to create expansive curtain walls and façades, a special set of guidelines apply. The linear glass segments are typically dual-glazed and limited to 4-m (13-ft) lengths, or the length specified in the manufacturer’s or supplier’s wind load charts for high-design-load areas. This precaution ensures horizontal channel glass segments have adequate structural support.
Specifically, since each channel glass segment rests on a padded, angle clip inside the frame member, it is independently supported from the other glass members within the framing system. As a result, it carries the dead load of the entire system from the jamb to the sill and can cause long-length channel glass members to deflect beyond what is acceptable. To extend the width beyond what is normally achievable, custom wind and dead load clips may be required for use at the intermediate point of horizontal glass installations.
