Energy Savings with Straw Bale Construction

In 1992, the Navajo Nation initiated a program to design and build sustainable, energy-efficient dwellings to address severe housing shortages on the reservation. Building Energy Measurement and Performance Analysis provided energy expertise at the initial design workshop and continues to supply technical support. As part of this program, a prototype house utilizing adobe and straw bale building technologies is under construction near Ganado, Arizona. The design reflects program goals of using locally available materials and labor and including Navajo architectural traditions. Straw bales for the prototype building came from nearby Navajo farms and were quickly assembled by untrained staff.

A wall is typically two feet thick, and with the reasonably good thermal characteristics of straw, has thermal resistance up to R60! Building Energy Measurement and Performance Analysis estimates that building heating loads could be decreased by about 15% for the range of climates on the Navajo reservation when using straw bale instead of an R-19 wood frame wall. Straw bales should also provide increased comfort benefits during warm weather. However, questions remain about the infiltration characteristics of straw bale construction and the potential for moisture migration into the wall, both of which could significantly reduce thermal performance.