Can Fully Glazed Curtainwalls Be Green?

http://blog.seriousmaterials.com/?p=415

Good-quality, thermally broken commercial windows typically have U-values of about 0.5...

Numerous studies have shown there are no daylight benefits with window-to-wall ratios over 60 percent, and in many cases 40 percent is optimum.

Even at these ratios, windows in a low-energy building should generally be triple-glazed, with large thermal breaks and some form of exterior shading (preferably operable)

In the end, glazing is a classic design problem that requires one to balance the desire for thermal comfort, energy efficiency, and light quality (all of which require small window areas) with the equally important desire for view, daylight, and connectivity with the outdoors (all of which benefit from large vision-glass areas).

Many designers have shown that beautiful and high-performance buildings can result from a proper balance.

All too often, however, it seems architects choose all-glass curtain walls 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.

http://greensource.construction.com/people/0807_opinion.asp

http://resourcecenter.pnl.gov/cocoon/morf/ResourceCenter/article/111

http://www.energycodes.gov/moodle/mod/resource/view.php?id=335

http://www.arca53.dsl.pipex.com/index_files/tt1.htm