SAN FRANCISCO -- At first glance, the big windows in the W Hotel's lobby look unremarkable. Then the sun strikes them -- and the glass slowly darkens to block the glare and heat.
The windows are made of Dynamic View Glass, created by View Inc. (www.viewglass.com), and represent a step forward for sustainable building. By letting users regulate how much light and heat enters a structure, they reduce energy use and eliminate the need for screens or blinds, the company said.
The technology still needs the test of time, but after five years of research and development, View launched the windows this month, describing the windows as a way to sheathe buildings in a "smart envelope."
"This is about energy efficiency, views and natural light," said View chief executive Rao Mulpuri. "It's a building designer's dream to be able to change the condition of a window as the outside world changes to maintain a comfortable level of light and temperature inside.
"Views and light make people happier and more productive, but today [without smart-glass technology] more glass means more energy consumption."
View, formerly Soladigm, will jostle with other smart-glass makers in an emerging market that, though tiny now, could hit $700 million a year by 2020, according to Pike Research. Its biggest competitor is SAGE Electrochromics, a Minnesota firm acquired by French industrial giant Saint-Gobain this year.
"Smart glass transforms glass from a passive building technology to an active one," said senior research analyst Eric Bloom with Pike Research and author of a recent study on the smart-glass industry. "It's the first innovation in the glazing industry in over 100 years."
The basic concept of smart glass is familiar to anyone who has worn transitional eyeglasses that automatically tint to sunglasses in the daylight. But the breakthrough by View and SAGE is to apply that idea to much larger pieces of glass -- 5 feet by 10 feet -- and to provide programmable controls. Both include GPS positioning to predict the sun's angle and intensity throughout the day.
Eyeglasses use a photochromic technique that directly responds to light; the smart-glass products are electrochromic, allowing them to be controlled based on a range of conditions.
Bloom said cost and long-term durability are roadblocks the industry must address.
"The life-cycle performance of the glass over time is a real concern," he said. "Because it's a new technology, no one has data on whether it will perform at the same level 10 years down the road."
As for cost, "smart glass represents a considerable premium of energy-efficient [double- and triple-paned] glass, which itself is a premium and can take 10 to 15 years to pay off in energy-efficiency gains," Bloom said.