The city of Santa Clarita, Calif., now possesses one of the world's only Gold LEED-certified straw-bale buildings. Completed in May 2006, the 12-acre Santa Clarita Transit Maintenance Facility includes a 22,000-square-foot administration building, 25,000-square-foot maintenance building, bus wash facility, compressed natural gas (CNG) fueling island for city buses, and publicly accessible CNG fueling station. The facility exceeds California Energy Efficiency Standards by more than 40 percent.

"One of the things that we brought to the table at the interview was our expertise with LEED and sustainable design principles," says HOK Vice President Charles Smith, AIA, LEED AP. "At our first meeting, we threw out a lot of different concepts that we wanted to pursue, but obviously the city had to buy into it." To prove to the city that straw-bale construction and other sustainable building strategies were viable and cost-effective solutions, the design team took them on a series of site visits in California and Utah to see the technologies at work.

Although the design team had not used straw-bale for construction in the past, they knew the owner hired a good contractor with a familiarity and understanding with the building material. Instead of using the straw-bale as structural, HOK decided to erect a post-and-beam structure using the straw-bale as infill. The walls are constructed so that there's a box beam built on 2x4s on the ground, which are filled with foam board. The contractor placed wire strapping underneath the box beam and then after they stacked the bales, they placed a wood box beam on top. They then wrapped the wire strapping from the bottom around the top beam and cinched down the straw-bale walls. The contractor then bolted the top box beam to 20-foot wood columns.

While straw-bale construction is the most unusual sustainable feature of this facility, the architect did employ a number of other sustainable strategies, including skylights and clerestory daylighting and a well-insulated "cool" roof with deep overhangs to shade clerestories and protect the walls from moisture.

Because of the necessary high-water use at the bus wash, water efficiency was a must. On-site stormwater collection and treatment, water-efficient plumbing fixtures, and a gray water reclamation system minimize water waste. Other features include an under-floor air system, water-source heat pumps, a courtyard and native plant garden, 25-percent fly-ash paving, and efficient use of local, recycled materials.

One of the more interesting aspects of the project is a huge photovoltaic array located on top of the bus parking pavilion. Because of the intensity of the desert sun, the buses needed a shading device. The architect created a dual-functioning shading and PV structure that allows the 12-acre facility to sell surplus electricity back to the local utility.

Source: "Spinning Straw into Gold," AIArchitect, January 29, 2007, by Heather Livingston. Read the story.