Serious Materials, manufacturer of sustainable building materials, has raised $19.8 million of an expected $56.2 million in a fourth round of venture funding, according to a filing with the SEC. The company develops energy-saving materials like drywall and windows to help buildings reduce energy use and cut costs.

The Sunnyvale, Calif. company has plans to replace the 6,514 windows in the Empire State Building by December 2010.  The work, which will be done at night, is part of a larger effort to decrease the building’s energy use by 38 percent.

The company, which last brought in $60 million in 2009, has raised more than $125 million to date. Investors include New Enterprise Associates, Foundation Capital, Mesirow Financial, Rustic Canyon Partners, EnerTech Capital, Navitas Capital, Cheyenne Partners, Saints Capital, VantagePoint Partners and Staenberg Ventures.