Let there be skylight at Mall of America's new atrium

The atrium at the Mall of America's new "front entrance" will be encased by a skylight of automatically tinting glass that's become a signature product of a Faribault window manufacturer.

The mall's decision to use the glass, called SageGlass, will provide comfort to shoppers, save energy and increase the flexibility of the space, executives said.

The glass was developed in Faribault by Sage Electrochromics, which was purchased in 2012 by a French building-products firm, Saint-Gobain, and now chiefly uses that company's name. Saint-Gobain announced the deal with the mall on Thursday at an architecture trade show in Chicago. Terms weren't disclosed.

The mall becomes one of the first high-profile, high-traffic places to use the glass, which has also been installed on a portion of St. Paul RiverCentre, a new building at the Argonne National Laboratory in Illinois and a renovation of one of the original buildings at the U.S. Naval Academy in Maryland, McDonough Hall.

"The Mall of America is going to be a marquee project," said Derek Malmquist, a marketer for Sage Electrochromics. "They want a nice front door and the natural daylight fits right into that."

Construction began in March on a $325 million addition and remodeling on the north side of the mall. In addition to a new entrance hall that will house luxury retailers, the addition will include a 14-story J.W. Marriott Hotel and a 180,000-square-foot, seven-story Class A office tower.

SageGlass will be used for windows and a skylight in the retail section of the addition, about 300 panes in all. Voltage running through the glass can be used to change its opacity. At the Mall of America, the SageGlass will generally be adjusted by light sensors, executives said, though building engineers will have the capability to directly change it as well.

Saint-Gobain estimates that the automatic tinting can reduce the cooling load of a given area by about 20 percent. At the Mall of America, the glass will give event planners the capability to change the lighting in the new atrium, darkening it, for instance, for a fashion show in the middle of the day.

"With SageGlass, we can control the amount of sun so that it is cool and comfortable in the mall whether it is 9 degrees or 90 degrees outside," Rich Hoge, vice president of operations for the Mall of America, said in a statement. "We'll also benefit from energy savings without having to block daylight with blinds or shades, which would have also been a challenge for us to clean and maintain in such a large, elevated skylight."

Sage Electrochromics first installed the automatically tinting glass in 2003 but was constrained for years by limits to the size of window pane that it could produce at its Faribault factory. With last year's completion of a $150 million, 320,000-square-foot expansion that's visible to motorists on Interstate 35, the company became capable of building larger panes that can take almost any shape.

"Now with the new plant, we have the capability to meet most architectural needs," Malmquist said. "Architects are asking us about bigger and bigger projects."

At the Mall of America, the company will deliver about 300 panes to cover an area of several thousand square feet. The atrium skylight, of course, is much smaller than the other 8 acres of skylights that use regular glass above the halls and amusement park at the mall. Converting those to automatically tinting glass "is a conversation for later," Malmquist said.

Evan Ramstad • 612-673-4241