Straw Bale Monitoring

Straw bale construction has the potential to provide beautiful, energy-efficient, environmentally progressive, easily constructed, and inexpensive housing. Straw bale construction could also provide a market for underutilized compressed agricultural fibers. However, fears about moisture penetration and resulting rot of the straw bales continue to hinder the acceptance of straw bale construction techniques. This project investigated the moisture levels of a straw bale building located in the southern Willamette valley of western Oregon to determine if there was sufficient moisture to promote fungus growth.

The walls of the straw bale dormitory at Aprovecho Research Center in Cottage Grove, Oregon, were instrumented with relative humidity and temperature sensors and monitored for a one-year period. Four sensors were placed in each of the east, west, north, and south facing walls, for a total of 16 wall sensor locations. We found that, while there is not a consensus among experts as to what level of moisture promotes fungus growth in straw bales, the upper end of the monitored conditions were within the zone in which fungus may begin to develop. Other factors, such as the period of time moisture levels remain above a particular level, may also play a part in determining the potential for fungal growth, and we concluded that further research is warranted.

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