The new science of glass
Glass architects and engineers are balancing aesthetics with performance.
Eighty-one years ago, architect Frank Lloyd Wright marveled at an old material that he helped give new meaning.Skip to next paragraph
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"What is this magic material, there but not seen if you are looking through it?" he asked in an essay. Mr. Wright responded to that question – one that has fascinated architects and engineers before and after his work – by calling glass a "supermaterial" and frequently incorporating it into his designs. With prescience, Wright believed that future buildings would be constructed where "Walls themselves because of glass will become windows and windows as we know them as holes in walls will be seen no more." Would Wright be surprised to see how his vision of glass architecture has come true in 2009?
The prevalence of towering glassy skyscrapers would probably not shock him – but the changing nature of glass itself might.
"Glass has become less about abetting observation; it is something to be observed in itself," explains Michael Bell, a professor of architecture at Columbia University, in his recent book and DVD "Engineered Transparency – The Technical, Visual, and Spatial Effects of Glass."
In a phone interview, Mr. Bell says that glass is no longer a single material, "but the name of the family of building materials 'rewritten' by new technologies."
Thanks to breakthroughs and continued stoking by architects, engineers have created glasses capable of things Wright would have never dared to attempt. In doing so, Bell says, "glass may have become something other than glass."
The traditional glass recipe – mix sand, soda powder, and quicklime, then heat until transparent – delivers unpredictable strength and fragility.
But in the 20th century, Wright and other architectural pioneers began designing buildings where interior daylight and landscape views were highly valued. To accommodate their imagination, architects urged engineers to craft new glass formulations with increased capacities to predictably perform structurally and artfully.
The age of skyscrapers became possible through the invention of strengthened glass able to bear ground and weather changes, and unforeseeable human activities.
To understand the demands placed upon glass in high-rise buildings, think of a car windshield: It consists of a sandwich of two layers of glass with a layer of a clear synthetic resin between. The resin layer seals the glass sheets together and, in the event of a crash, prevents them from breaking into tiny shards. These "interlayers" have since contributed to novel "hybrid glass," possessing previously unimaginable strength under enormous loads.
In the 21st century, innovative glass technology has been driven by concerns with climate change, energy conservation, and urban sustainability.
For example, the heating and cooling needs of American buildings amount to an enormous collective energy bill – and estimates say one-third of a building's energy expenditure comes from heat seeping through traditional windows. Conversely, window glass can intensify the sun's rays during summer, forcing millions to reach for the air conditioner.
However, by using argon or krypton gas between glass panes, solar heat can be better managed.
Another technological wonder is "smart glass," or to use the proper term, "electrochromatic glass."
It is coated architectural glass that changes its properties from moment to moment depending on changing light conditions. Under direct light, the panes darken, controlling how much glare and heat pour through the windows without relying on curtains or blinds that can obstruct views.
"Self-cleaning glass" comes coated with a thin layer of titanium oxide that is activated by the sun's ultraviolet rays. The resulting reaction causes dirt on the window to dissolve. The titanium coating also stops raindrops from beading, thus reducing spotting.
These innovations in glass technology come with a price – literal as well as artistic.
"Each manipulation for improved energy performance makes glass less like glass and more like other nontransparent materials, such as metals, ceramics, and stone," said architect and consultant Robert Heintges at the 2007 Columbia University conference on glass in architecture that inspired Bell's book and DVD.