Cities like Toronto, New York or Chicago get cold in the winter and hot in the summer, yet almost every new condo and office building is designed with floor to ceiling glass. Something many people don't realize that the more glass a building has, the less strength there is in the outer walls. All-glass buildings develop envelope problems much sooner than traditional designs.
Andrew Michler calls it "the very contagious disease waytoomuchglassia." At Building Science, John Straube does the math and shows how really bad they are. He explains:
Glazing systems, including almost all modern high-performance ones, have very little ability to control heat flow and solar radiation. Older windows also did little to control heat loss and solar gain. Hence, most older buildings had restrained window-to-wall area ratios. Most of the tremendous performance gains in glazing technology over the past 25 years have been squandered on increased window area, not improved performance.
He goes on to explain that there is a balance that has to be found, between maximizing daylight but minimizing unwanted heat gain or loss. Straube also points out that there are some expensive, high quality assemblies that can get up to R-12. But most of these window walls thrown up on condos have the R-value equivalent of 1/2" of fiberglass. (R-2). Who would build a house with that? Straube concludes:
Many designers have shown that beautiful and high-performance buildings can result from a proper balance of glazing quantity and quality. All too often, however, designers appear to choose all-glass curtain walls or floor-to-ceiling strip windows because they make it easy to create a sleek impression while leaving all the tricky details in the hands of the manufacturers. How much longer can we afford to pay the energy bills that result from that choice? It’s high time to revive the craft of designing beautiful facades that don’t cost the earth.
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