Sage Electrochemics makes a thin-film window glaze that changes tint throughout the day to let in an optimal amount of light and selectively trap the sun’s rays to heat or cool green buildings. The Fairbault, Minn. company just brought in $20 million in a third round of funding led by Good Energies and joined by existing investors Applied Ventures and Bekaert.

It claims that its product, called SageGlass, can slash energy bills for facilities accustomed to shelling out large amounts for heating, air conditioning and lighting. And it’s not just guesswork at this point — Sage has applied its coatings to windows at several educational institutions, hotels and even a residence. It charges about $2,000 to coat skylights and up to $500,000 for large-scale commercial installations.

The new investment will go toward the construction of a SageGlass factory with a $120 million price tag. To foot the rest of the bill, the company nabbed a $65 million grant from the Department of Energy but has yet to receive it. It will also look to raise another $35 million in equity. Sage also stands to benefit from the economic stimulus package, which includes government incentives to retrofit federal buildings for greater energy efficiency. The company has brought in $57 million in capital to date.