Soladigm, the Milpitas, Calif.-based startup with windows that change color and tint to save energy in big buildings, has raised a $55 million Series D round, bringing its total VC haul to $125 million. The round was co-led by Reinet Investments and NanoDimension, and included previous investors DBL Investors, GE, Khosla Ventures, Navitas Capital, Sigma Partners, and The Westly Group.

It’s a lot of money, but then, building factories to churn out self-shading glass is an expensive proposition. Soladigm, which also raised $4.5 million in debt last month, has a manufacturing facility in Olive Branch, Miss. that cost about $130 million to build.

Soladigm is also partnering with glass giant Guardian Industries, which is carrying Soladigm electrochromics in its portfolio. These kinds of partnerships will be important, as one of its rivals, Sage Electrochromics, was acquired by French glass giant Saint-Gobain for an undisclosed sum in May. Saint-Gobain also put $80 million into Sage in 2010, on top of a $16 million round in 2007 from Good Energies, Applied Ventures, NV Bekaert, and Bekaert Corp.

Electrochromic glass changes color or opacity under different electrical conditions, allowing you to darken windows to block hot afternoon glare, make them clear to let in warming winter sun, and other such energy-saving features.

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