San Mateo County Office of Education's Outdoor Education Program built the county's first permitted straw bale building using a local contractor and five weekend volunteer workshops. The goal was to create a model for San Mateo County of alternative building with sustainable materials, as well as an indoor classroom and teaching tool for the students of Outdoor Education. Take a moment to view our step-by-step, bale-by-bale construction of this energy efficient and totally unique structure.

Why use straw bales? Straw is an agricultural waste product that is typically burned, creating air pollution and health risks for people who live in the area. Instead of burning some of these straw bales, they are used as the walls of the building. They have incredible insulation properties, with an insulation benefit of R40-60, while a typical house has an insulation benefit of R19. Already, the SMOE Straw Bale Classroom has maintained a rather constant inside temperature of 60°F to 75°F, while the outside temperature fluctuated between 29ºF and 85ºF.

How is the straw bale building capable of retaining so much heat? The answer lies in its passive solar design, which requires minimal energy to heat and cool. The design includes correct site orientation, double-paned windows, and overhangs. Furthermore, the cement slab floor serves as the thermal mass that regulates the temperature. The floor is also stained a dark color in order to help it absorb heat.

The frame of the straw bale house is built with 80% recycled lumber. Diverting this lumber from the landfill is an example of a sustainable practice, as most construction waste is not reused. In fact, nearly one quarter of the waste in San Mateo County landfills is from construction waste.

The straw walls are covered with earth plaster on both the inside and outside. This plaster is made from natural materials — clay, straw, and sand. The roof is painted with a nontoxic milk-based paint.

The energy for the lighting in the Straw Bale Classroom comes from solar panels on the roof and a nearby wind generator. These solar panels are also responsible for powering an interactive solar energy display and the charging of Outdoor Education's electric vehicle.

Due to the simple nature of these building processes, the workshops to complete this building inspired community development. The Outdoor Education staff and other community members of all ages were brought together to learn alternative building techniques through actual participation.