The AIA's Soloso publication profiles HOK's design of the 56,000-sq.-ft. Santa Clarita Transit Maintenance Facility.

Designed by HOK Los Angeles and completed in May 2006, the facility exceeds California Energy Code Title 24 for energy conservation requirements by 44 percent.

In addition to the straw bale walls, the architects specified a well-insulated cool roof and high-performance glazing to achieve a super-insulated envelope. This combined with other environmentally-friendly features such as nighttime ventilation, daylighting strategies, fly-ash content in concrete pavement, and bike storage and showers for employees, resulting in a LEED® Gold rating.

To allay moisture concerns, electronic monitors in the bales under each window sill are tied back to computers with alarms.

“The lime plaster finish is porous and breaths to release built-up moisture,” said Charles R. Smith Jr., AIA, senior project manager at HOK. “If the moisture level exceeds 20 percent, the cause of the moisture build-up (most likely a broken water pipe since the walls are protected from normal weather) would need to be determined and the affected wall area would need to be removed.” During construction, a roofing contractor’s mistake resulted in water damage requiring the replacement of 60 percent of the bales.

Straw bales are a sustainable material in several ways: Straw is an agricultural waste product; a renewable resource; locally available; and has great insulating properties. Comparable in R-value per inch to fiberglass batt insulation, its thickness can result in R-42 to R-70 walls, depending on bale density.

Source: "Straw Bale Construction in Large-Scale Buildings," AIA Soloso™, August 2007, by Linda Reeder, AIA, LEED AP. Read the story.