Spring 2004

Glazed Over
Recent Trends in Structural Glass
by Timm Walker

I recently spoke with a fellow architect about an impressive project in design development involving an advanced glazing solution. He told me that he was interested in using something other than the “ubiquitous” point-supported glass. I thought to myself, how could an architect consider point-supported glass ubiquitous? I asked him if he considered aluminum curtainwall ubiquitous. He simply shrugged his shoulders. We discussed a handful of glazing possibilities, but ultimately he designed that very project with point-supported glass. He did, however, make me think about alternatives in structural glazing.

Without fail, architects strive to design facilities in a way that creates a work of art for their clients and/or the end user. We desire to create buildings with which people can identify; a project that everyone knows by name because the public finds it so interesting and appealing. Architects who specialize in corporate facilities and speculative office buildings strive to design “thee address” for their clients. “Thee address” is where a potential tenant wants and needs to have his office. There have been some noticeable trends in structural glass design over the last five years in the United States. Let’s consider a few of those possibilities.

Point-Supported Glass
Point-supported glass is considered cutting-edge technology by many architects. It is frameless with a variety of structural support methodologies including a pipe column, glass fin, fish truss and cable net, just to name a few. Although the cost is understandably higher than aluminum framed glazing, the beauty and drama created by point-supported glass can be quite powerful. Because of its high level of transparency, architects choose to utilize point-supported glass when they want to make the sky seem as though it lives in the lobby of a building. Those same architects may choose to utilize point-supported glass when they want a retailer’s goods to seemingly flow onto a busy street corner.

Clamped Glass
Instead of penetrating glass panels in their corners, clamped glass or patch-fitted systems make their connection at the common intersection of joints where four glass panels meet. The shape, design and finish of the patch fitting is up to the designer. Patch fittings might be square, round, elliptical, butterfly shaped or virtually any shape an architect can concoct. Similar structural back-up systems can be employed for point-supported glass or patch-fitted systems (pipe column, glass fin, fish truss cable net, etc.).

Cable Net Walls
Architects increasingly have become interested in glazed cable net walls over the last five years. Cable net walls are often the most costly—and the most transparent—advanced glazing solution available. The structural support system often consists of a ¾-inch stainless steel cable that all but disappears behind the ¾-inch glass joint. Those cables could be vertical, horizontal or both if employed in a wall. Two U.S. designers pushing the envelope in cable net walls are James Carpenter with his design of the IDX Tower in Seattle and Lohan Caprile Goettsch with the design of 111 South Wacker in Chicago.

Line-Supported Glazing, 
Line-supported glazing, often referred to as vario-clip, is also gaining in popularity. It is a glazing solution that offers a balance between aluminum curtainwall and point-supported glass with regard to transparency and cost. Line-supported glazing often results in a horizontal mullion with a butt-glazed vertical. Line-supported glazing provides architects with a high-end glazing solution at a lower cost than point-supported glass. 

Architects have also become enamored with large glass panels. Cesar Pelli, for example, recently completed Overture Hall in Madison, Wis., with insulating glass panels 9-feet tall and 17-feet wide—some of the largest insulating glass panels in North America. In addition to their enormous size, these insulating glass panels were line-supported for high visual transparency. 

SOM also designed a point-supported glass wall for a Chicago project that will be 14-feet tall with a white custom frit that will be back lit with changing colors.

Adding Color
While structural glass has long been kept as transparent as possible, architects are starting to design more with color, texture and pattern, using frit and/or interlayers. Richter Cornbrooks Gribble, for example, designed the Star Spangled Banner House in Baltimore with line frit in red, white and blue to create a large rendition of an early American Flag.

Double Glazing
Europeans have incorporated double-glazed technology in their glass walls for years. This technology relies upon two surfaces of glass with an airspace between glass lites that could be anywhere from 12 to 42 inches. Obviously, with twice the glass there are additional costs, but the initial investment in a mechanical system is lower. Furthermore, annual energy costs could decrease dramatically. This type of technology in the United States may soon follow Europe where fuel costs are dramatically higher.

Grid Shells 
While grid shells (curved surfaces) have been used by architects overseas, there usage is starting to emerge in the United States. The organic, free-form and flowing structure of a grid shell is another feat of design and engineering. HOK, for example, recently designed such a project that will be constructed and completed in 2005 at the Wrigley Building in Chicago. 

These are just a few trends in structural glass design. Due to the higher cost of structural glass systems versus aluminum curtainwall, architects tend to use their resources wisely. For example, an architect might enclose a building in aluminum framed glass curtainwall and utilize an advanced glazing solution, such as point-supported glass, where people enter the building. Placing such a system in a high focal area, such as an atrium, lobby or main entry of a building, gives the architect “the most bang for the buck.” 

Countless glazing solutions are available to architects—even when budget is a concern. But, is point-supported glass ubiquitous? I think not.

Architect's Guide to Glass & Metal