Old Main is the first construction experiment on campus. The intent was to create combination office space and living space, so it features a large kitchen and cob-constructed bathtub. It is now used for offices and meeting space, hosting many gatherings and community events. 

The building is traditional straw bale and cob construction, with walls three feet thick and large double-pane windows. Facing south, it takes advantage of passive solar heat supplemented by in-floor heat. An overhanging roof keeps the sun out in summer, while allowing the low sun of winter to warm the building. A well water cooling system helps keep the building comfortable throughout the summer months. The mud used included a mix of recycled paper and shredded straw. 

​

Because it's fun to play with mud, cob sculptures and design features are everywhere. Visitors marvel at the cob wildlife scenes, the window wings, and the Egyptian bathroom. Even the stairs and floors are made of cob. (see photos below)