Saint Gobain invests in self-tinting 'smart glass'

Building materials heavyweight Saint Gobain yesterday bought a stake in glass specialist Sage Electrochromics and plans to build a large factory to make automatically tinting glass.

France-based Saint Gobain paid $80 million for a 50 percent stake in Faribault, Minn.-based Sage Electrochromics, which makes energy-saving windows and skylights. The deal represents a significant boost for the green building technology.

These two images show a building interior that uses Sage's electrochromic tinting glass.

With electrochromic glass, also called "smart glass," a low-voltage current causes windows to tint based on incoming light. Automatically adjusting the amount of sunlight that comes into buildings can significantly save on energy costs with a reduced lighting and climate control load.

Because of the added cost of the coating material, electrochromic glass has seen limited use. With its investment in Sage, Saint Gobain said it intends to scale up manufacturing to bring down the cost.

Later this month, it intends to start construction of a $135 million electrochromic glass plant in Faribault that will have a capacity of 4 million square feet per year and be able to make larger sheets of glass than currently available. Production is planned to start in the middle of 2012.

 "This alliance will dramatically accelerate global adoption of this game-changing technology in both commercial and residential markets," Sage CEO John Van Dine said in a statement.

In that statement, U.S. Department of Energy Secretary Steven Chu said research shows that Sage's glass products can lower the cooling load of commercial buildings by 20 percent and lighting by up to 60 percent. Buildings designers can also buy cooling and heating equipment that is up to 25 percent smaller. The DOE provided Sage with $72 million in conditional loan guarantees.

Soladigm, a Silicon Valley smart glass start-up, earlier this year said that it secured a state loan in Mississippi to build an electrochromic glass factory.