Light inspires energy efficient building design

Artists find inspiration in many ways. But for the artists (architects and researchers) working collaboratively to create the most energy efficient office space in the U.S., the inspiration was simply light. In fact, light and the access to light turned out to be a top factor when designing the U.S. Department of Energy's (DOE) Research Support Facility (RSF) located on NREL's South Table Mountain Campus near Golden, Colo.

"One of the most powerful drivers in the project is daylight," Philip Macey, RSF project manager for Haselden, said. "It's the reason why the building is fairly slim from front to back and long. Daylight and solar energy are at the core of the building and the windows are the vehicle that gets the daylight into the building."

Scheduled to open this summer, the 222,000 square-foot RSF will house more than 800 staff and an energy efficient information technology data center. Because 19 percent of the country's energy is used by commercial buildings, DOE plans to make this facility a showcase for energy efficiency. DOE hopes the design of the RSF will be replicated by the building industry and help reduce the nation's energy consumption by changing the way commercial buildings are designed and built.

Size Matters

In order to draw as much light into the building as possible, designers looked at a variety of window sizes and glass combinations that would maximize the amount of light, reduce glare and prevent heat from entering and escaping the building.

"There's this push and pull between the size and the construction of the window and getting all of the benefits of daylight into the building," Macey said.

According to Macey, the team spent a good deal of time deciphering which windows would be just the right size. "The south side RSF windows are a little smaller than the north side windows," Macey said. "That was so we could get the light to come into the building in just the right way. On the north side, the glass goes up considerably higher and that's because north light is really gentle. It's soft and diffuse and there really isn't much direct sun. The south side requires a lot more attention because you can get direct sunlight — and it's typically not helpful when it comes to conserving energy.

"The windows are literally the balance point in how the building manages energy. Get the windows too big and you'll get too much heat gain and heat loss. Too small and you won't get enough daylight to light the interior of the building to the middle of the floor plan. You want to have nice even, balanced light across the floor plan."

To help boost the light to the middle of the office space, some of the windows have "light louvers" inside the widow. The light louvers look like a mini venetian blinds hung upside down in the window. The curve of the blind catches the light and bounces it very deep into the building. By literally helping to toss the light across the room, designers were able to maximize the sunlight increasing its distance from 20 feet to 30 feet inside the office.

The windows in the RSF will also serve double duty as a working part of the buildings' ventilation system. To help cool things down in the summer, employees will get notification to open windows to let cool air in or to shut windows to keep warm air out. While the windows and the louvers are fairly low tech solutions, the windows on the west and eastern exposures will look to new technologies to help the building conserve energy.

Read more at http://www.nrel.gov/features/20100301_windows.html.