Straw Bale At Work

In the back corner of the yard stands a testament to Candace’s dedication to both teaching and learning about sustainability. In 1997, she designed a load-bearing straw bale building. She and her students built the 10-by-12-foot structure from renewable and recycled materials as a research project. The goal was to test straw bale construction and other eco-building techniques against the climate conditions in the Pacific Northwest.

Reclaimed concrete from a dump site and old tires helped form the foundation. A layer of decking made from a recycled wood/plastic product, paired with a rubber sealant and 30-pound felt paper, provided a moisture break between the foundation and the 42 straw bales that form the walls.

The bales were stacked five high and covered with a box beam of 2- by 6-inch boards and CDX plywood filled with straw flakes for insulation. Seven trusses, formed from 2 by 6s, made up the roof—complete with a built-in trough to catch water in a 180-gallon collection system.

The windows and door openings were wrapped with 30-pound felt paper. The straw bales were covered in coconut fiber, which gave a surface to apply the stucco—a mix of clay, clean soil, cement, fine sand, linseed oil, skim milk (for casein), water, and chopped straw. A thin cement stucco mixed with ochre pigment finished off the exterior. Before plastering, Candace placed 12 manual-read moisture sensors within the bales so she could monitor moisture at various points within the wall structure.

Reclaimed bricks laid over tamped sand make up the interior floor. Beneath that, a layer of recycled nylon sand bags on top of a 3-inch layer of river rock creates 18 inches of thermal mass for the floor.

The success of the project prompted Candace to convert her garage into an eco-friendlier studio by infilling the north and west interior walls with straw bales. Overhead rafters were used as a box beam to attach bamboo pins, and the straw bales were covered with burlap—instead of wire mesh—as an experiment to see how well fibers and plasters would adhere together. Candace brushed three layers of plaster made of earth and lime onto the burlap, and covered the burlap with reed matting. Six moisture sensors monitor moisture in the straw-bale walls. Renewable and recyclable materials complete the décor—bamboo flooring, a ship-bath with dual-flow toilet, interlocking floor mats made from old tires.

The finished garage served as a studio until Candace moved her work space into the straw bale building in the backyard. She renovated the 300-square-foot garage space into a one-bedroom apartment, designing with the principles of efficiency.